So you new to computers in general, or new to social networks like FaceBook? If so, listen up. One of the ways the bad guys take advantage of people is to take advantage of the trust factor that is built up with social networks.
How can this happen? Let's just say you happen to go to a website....say usatoday.com. And lets say you just happen to be unlucky and an ad that flashes up on the usatoday.com site happens to be one that the criminal bad guy has taken advantage of and planted a redirect that takes you to a site that runs the latest and greatest attacks on your computer. Could be a malformed PDF, Word, or Excel document. Next thing you know, your PC is being watched by the bad guy.
After a PC is has been infected with malicious software (Malware), some of the things bad guys try and steal are e-mail accounts, social network accounts, etc. Along with these of course, they also are looking for banking credentials, credit card credentials too. Now what? The bad guy has to keep spreading his malicious software around and take over more and more computers. This is how they continue to exist. Computers get cleaned from time to time so they are always looking to take advantage of people and tricking them to go places they really shouldn't go and take control of new computers.
With someone else's Facebook signon credentials, they can now send a message to all of your contacts with a link to a malicious website. Your friends trust you, so your friends click and BAM! They are now under the control of the bad guy and this scenario just continues to roll along. So, my advice to you is this when it comes to links sent from friends. DON'T CLICK ON THEM!!
Hang in there. Have fun, but be safe. Have a great weekend!