You can access Facebook features using a mobile device like a cell phone in three ways: mobile text messages, mobile uploads and mobile Web browsing. Let's take a look at each of these in turn.
Text messages use a standardized mobile text transfer method called Short Message Service (SMS) or Multimedia Messaging Service (MMS). SMS allows you to send and receive text messages to services like Web sites, voice-mail systems and e-mail servers. An SMS message can only be up to 160 characters long. The MMS standard is an improvement on SMS, with no size limit to messages (though very large messages require an advanced 3G phone network to transfer through the system). Not all phones have SMS or MMS capabilities.
When you send a text message from your phone to Facebook, the message transmits to a mobile switching center (MSC), which sends the signal to a signal transfer point (STP). From there, the message goes to a short message service center (SMSC), which then sends the text to Facebook. When Facebook sends a message to your phone, the process is reversed. Using text messages, you can look up basic member profile information, send messages (including pokes and wall posts), add friends to your network and interact with some Facebook applications.
Mobile uploads work in a similar way to text messages, but must use MMS. MMS allows you to send not only text, but also sound files, video and images. The transfer method is similar to SMS, but it requires a handheld device compatible with the MMS standard. Because some devices aren't MMS compatible, service providers sometimes build in a feature that alerts a user when he or she has received a multimedia message. The message usually tells the user to visit a Web page link to view the message.
With MMS messages sent from your phone, you can upload photos to your profile -- they'll appear in a special uploaded photos section. You can also upload notes or videos from your phone to your profile. In either case, you must create your multimedia message first, then send it to the appropriate e-mail address.
Your phone must have Web browsing capabilities in order for you to visit Facebook from it. You'll need to direct your phone's browser to m.facebook.com, Facebook's site designed specifically for mobile browsing. To upload notes to Facebook, you send the message to email@example.com. For photos or videos, you send the message to firstname.lastname@example.org.
Unlike typical Facebook pages, the mobile counterpart's code is in Extensible HyperText Markup Language (XHTML). XHTML is a more restricted language than standard HTML. One of the reasons for this is that the World Wide Web Consortium (W3C), an international organization that develops interoperable technologies for the Web, recognized the need for a Web language that mobile devices could easily interpret. Computers have more resources than mobile devices, and can interpret much more complex Web pages than a cell phone or similar gadget. XHTML helps to level the playing field.
In the next section, we'll look at some of Facebook's impressive statistics.