What is the difference between the wall and the timeline? How do these two behave differently? Also, what is the difference between the wall and the news feed? Also, is the mini feed and activity log the same thing? Also, what is FBML?
The wall is basically the old name for the Timeline, when Facebook introduced Timeline, they renamed the wall Timeline.
The newsfeed is a stream of your friends Facebook activities. Your wall (aka Timeline) is your own list of activities you have carried out on Facebook.
The mini feed is also known as the Ticker bar, that shows a "real time" condensed stream of what your friends are "liking", "commenting on", "posting", "attending" etc, in a narrow column to the right of your newsfeed. The activity log shows a list of activities you have done on Facebook, including things you have liked, commented on, been tagged in, etc and lets you either delete those activities or limit their visibility on your timeline.
FBML was a web page layout language based on HTML, used for creating content on Fan Page applications, Facebook have phased this technology out now.
The news feed is what shows up in the central content column of Facebook once you log in (or when you click on Home in the header links) and consists of a sequence of algorithmically selected posts in reverse chronological order which your friends have posted on their timelines (either by uploading content or sharing content found on other people's timelines), or which someone has posted on one of your friends' timeline (again by uploading or sharing), or which a friend has posted on your timeline (again by uploading or sharing). Another way to make something show up in all of your friends' news feed is to "Like" something (likes also show up in your activity log but not in your timeline).
The activity log (accessed by first loading your profile page by either clicking on your name in the header links, or on your name in the left sidebar, and then clicking on the View Activity Log), displays all your activities and activities by your friends related to you in reverse chronological order. The activity log replaces what used to be called the mini feed. The timeline on the other hand replaces what used to be called the wall. The timeline is where all your posts go. The timeline is shown by default in the central content column of Facebook when you access your profile by clicking on your name. As far as I can tell the timeline will contain a subset of information appearing on the activity log.
FBML was a restricted version of HTML for Facebook used to format text in posts which is no longer in use. When people make posts they can tag you with a Twitter handle (an @ followed by your name) to make the post show up on your timeline. You may delete posts from your timeline as desired by clicking the small 'x' icon on the upper-right hand side of each timeline item.
People can also embed hashtags in messages (consisting of the # key followed by a keyword) to allow such content to be indexed for searches that make use of such hashtag.
I found some of the answers to my question on Wikipedia, and others by playing around with the Facebook interface.