Google, the most popular website on earth, is worried about the second most popular site. That, of course, would be Facebook. Why else would Google keep trying, over and over again, to create a social network of the same type?

Orkut, Jaiku, Wave, Buzz — Google has lobbed forth one fizzled flop after another. And now there’s Google+. It’s the latest Google “we wanna be Facebook” project.

The difference is, this one’s got a real shot. Instead of throwing open its doors with a big splash, as it did with the hopelessly confusing Wave and the privacy-challenged Buzz, Google is letting Google+ seep into the world virally.

You can’t yet just go sign up; you have to be invited by someone who’s already a member. Even so, Google+ already has millions of members. That’s not quite 750 million (Facebook’s current tally), but watch out for the network effect.

At first, Google+ looks like a shameless Facebook duplicate. There’s a place for you to make Posts (your thoughts and news, like Facebook’s Wall); there’s a Stream (an endless scrolling page of your friends’ posts, like Facebook’s News Feed); and even a little +1 button (a clone of Facebook’s Like button), which may be where Google+ gets its peculiar name. But there’s one towering, brilliant difference: Circles.

On Google+, you put the people of your life’s different social circles into — well, into Circles. That is, groups. Categories. Google starts you off with empty circles called Friends, Acquaintances, Family and Following (people you don’t know, but want to follow, as you would on Twitter). It’s a piece of cake to add new ones. They can be tiny circles (“Granny and Gramps”) or big ones (“Family Tree “), organisation-based (“Fantasy League Buddies”) or arbitrary (“Annoying People”).

Creating them is a blast: an array of tiles represents your online acquaintances, which it assembles from Gmail and other accounts. You drag each into an on-screen circle, where they tumble into place. You can drag a person into more than one circle. The lucky encircled friend will know that you’ve added him or her to a circle, but not which one, thank heaven. From now on, every time you share something – a news item, a thought, a photo, a chat invitation -you can specify exactly which Circles receive it.
In one fell swoop, Google has solved the layers-of-privacy problem that has dogged Facebook for years. Senators embarrassed by their children’s drunken party photos. Potential employers reading about your crazy nightlife. Girlfriends learning accidentally about their beaus’ proposal plans. All of it goes away with Circles.

You share each item with only the people who deserve to know. And simultaneously, you spare the masses from seeing news of no interest to them; why should the whole world be in on your discussion of this Friday’s bowling outing? You’re spared, too. You can click a Circle’s name to filter the scrolling blurbs. You can view only the work-related posts or only your college buddies’ posts with one click apiece.

Facebook has something similar, called Lists. But compared with Circles, it’s buried and a lot more effort to use. In Google+, you have to specify who gets each post or each photo (although it remembers your last selections). That’s actually a little annoying — you can’t just type an update and hit Enter — but over all, the benefits outweigh the hassle.

Google+ has a few more attractions, though, besides this clever privacy control feature. There’s Sparks, which is like a personal press-clipping service (and akin to Google Alerts). You browse for, or type in, a topic you’re interested in, like “Electric Cars,” or “Bundt Cakes.”

Google+ fills the screen with matching articles, news and videos from all over the Web. It may be the easiest, least threatening news reader in history. The most mind-blowing “Facebook can’t do this” feature, though, is Hangouts. Technically, it’s videoconferencing. It lets up to 10 people join a chat simultaneously, using their Web cams or laptop cameras.

A row of one-inch tiles, each displaying one participant’s video feed, appears below the big screen. Google+ does its best to switch cameras for the big screen automatically, based on whoever’s talking at the moment. (You can also click tiles manually.)

A skinny chat window appears on one side for typed remarks, and a YouTube button lets everyone watch YouTube videos simultaneously on the big screen. Slick. It may sound like Skype or iChat (or Facebook’s comparatively lame, justannounced, one-person-at-a-time video chat feature). But its integration with the rest of Google+ makes it much better. You can see when one of your buddies is in a video hangout, so you can “drop by.” Similarly, when you’re feeling social, you can click Start a Hangout, announce its availability to a particular Circle of friends , and let them drop in to visit you.

A video chat doesn’t have to be a scheduled, formal deal. It’s always on the Web, so you don’t have to install a program. It’s available to your Circles, so you can whip together a quick chat to organize a party or a tennis match. And it could do just fine for many business meetings (or even business trips). You can share Photos easily by dragging them from your computer right into the box where you’d type your latest news. And you view other people’s photos in a beautiful, black-background gallery, with comments off to the right.

If you have an Android phone, even more fun awaits. There are Huddles (instant phone-to-phone group chats with your Circles). And when you take a picture with your phone, it’s auto-uploaded to a private holding area on your Google+ page.

Later, you can share them with the appropriate social circles. Now, there are, of course, a few minuses to Google+. Perhaps because of its newness, Google+ feels uncluttered and calm, especially compared to the frenetic, commercial Times Square of Facebook. But Google+ still is, in its way, just as confusing. You keep wondering: What if people in that circle share my private post with their circles?

And what happens if I remove a couple of people from a circle? Can they still see things I’ve shared in the past? You’ll spend a good deal of time fumbling around. No other services (like Twitter or, of course, Facebook) are tied in yet. No games or applications yet.

The members so far are mostly geeks. There are bugs and glitches, although it would be unfair to mention them; the service isn’t even public yet. And we can probably look past Google’s bizarre promotional/tutorial videos, whose narrators seem to have been hired from the Society for the Advancement of the Inarticulate. (Actual transcript: “And, the friends you have are, kind of the ones you have that, allow you to, like, geek out about the things that you were absolutely passionate about.

And that’s the reason you stay friends with them, is not because you’re talking about things with them to talk about things that interest them, it’s because it interests you and you’re absolutely passionate about it and they have enough of a commonality to let you explore it.”) But Google calls Google+ a project, and that’s just what it is, an unapologetic beginning.

It’s online, so Google can and will constantly fine-tune it, add features and beef up the help mechanisms. Until now, Facebook and Twitter have been the Dominant Duo of social networking. But Google’s less sprawling, more video-centric, better-controlled new service is already too good to ignore. Now it’s the Dominant Duo …+1.