It has gps hardware built in, it doesn't require wifi or a cell connection (like many cell phones that make use of the cell towers, called, "aGPS" for "assisted GPS") to determine your position. aGPS is faster to find you, but then you need to have cell coverage. You'll need to download MAPS to your Playbook before using it if you what it to show where you are on a map. I use the free Playbook app, "Osmand" which makes use of free open source maps. There are other available free GPS apps that provide other features. Because this is not aGPS it might not be able to find the GPS signal if you're indoors, some people have success others don't, but this isn't all that uncommon for GPS. In case you're wondering I'm using a Wi-Fi only Playbook.
It does not work without a WIFI. On the go, as a mobile application, you must have MIFI along with data subscription (alternately, you must "bridge" it to a Blackberry phone with data . Once it locates itself (which takes 2-5 minutes) it works fairly decently, albeit slowly. Of course all this information is not available from RIM before you buy the tablet.
First set up a seperate tethering plan with your cell phone provider. Then download blackberry bridge in both your blackberry cellphone, and playbook. Open bridge and link your cell phone with your playbook. Once you are linked, use you cellphone touchpad or curveball depending on your phone to control the ball. Put the arrow on the gps app to open it. From here, you should be able to use the gps.