All the online guesswork over the past few days was correct: Facebook has launched its own location features on the world’s largest social network. Facebook founder and CEO Mark Zuckerberg, wearing jeans but eschewing his signature hoody for a grey t-shirt, introduced the new feature at a press conference at Facebook’s headquarters in Palo Alto, CA, Wednesday afternoon.

“There are three main things that we are trying to do with Places,” Zuckerberg told a crowd of press and Facebook employees. “Help people share where they are in a nice and social way; show who is around you; and finally help you to you see what is going on, and to help you discover new places and things to do.”

The team that developed Places over the last nine months showed how that is done, primarily through tagging and commenting. You arrive at a restaurant and “check-in.” You then have the option of tagging those friends who are also with you. As you and your friend check-in places, the activity shows up in the Facebook newsfeed. As with all things Facebook, users will have to decide who gets to see this new layer of geographic information, or whether it is made available at all.

As months and years roll on, all the people that showed up — the things that occurred, the good meals eaten and bad cocktails consumed — have the potential to become associated with a physical place. “One day, these pages will be our collective memory,” said Facebook’s VP of Product Chris Cox. “That’s dope.”

Facebook Places will be available starting Thursday throughout the United States. When you log into Facebook from a desktop or notebook computer you will see a new “Places” tab that will be the home for all the new geographic information you and your friends will be generating. Where it gets really powerful, of course, is when the feature is enabled on mobile devices. Support for Places on the iPhone went live Wednesday night. Support for Android phones and Blackberry is in the works, but there is no specific timeline for their launch. In the meantime, Facebook engineers suggest using the “touch” website on Facebook.com.

Location, location, location

Location services like Foursquare and Gowalla in particular have been getting a lot of attention recently, and the obvious question is does this mean their end? Facebook has done this before — integrating popular features like photos and the newsfeed, developed by outsiders, into the main Facebook product. In this case, Zuckerberg stressed that what Facebook is offering is substantially different from other services out there. The implication being that they can continue to keep their users happy while more tightly integrating with Facebook. To that end, Facebook is offering an API so that partners can layer their own services on top of Places.

Both Gowalla and Foursquare presented their ideas Wednesday for how that will happen. Other launch partners include Yelp and Booyah. The allure for all these independent players, who it should be noted have already integrated their services with Facebook, is 500 million-plus potential users. The risk, of course, is that Facebookers will abandon the passport stamps, badges and honorifics they collect in Gowalla, Foursquare and other services for Facebook’s approach.

Still, Facebook has been very successful helping other companies drive business on top of its core platform — casual gaming company Zynga being the most obvious and lucrative example. With its launch Wednesday, Facebook clearly aims to be the hub around which all kinds of location services function. Given its enormous center of gravity for all things social, it has the potential to be an enormous winner here, though Google (GOOG) will no doubt have something to say about that.

The question of how Facebook will make money on all this went unanswered by Zuckerberg. You can imagine all sorts of local advertising tie-ins, coupons and offers depending on where you are and what you like. Those are all possibilities, Zuckerberg allowed, “but for this first launch, we wanted to do three good use-cases really well, including having a good API.” Apparently the money will come later.

Zuckerberg also offered a bit of a teaser. “This is going to be a really fun and interesting summer, we have a lot of products we are building,” Zuckerberg said. “There are going to be a lot more launch nights this summer.”