there are a few desktop recorder packages (for both Xsessions, and terminal sessions) that can record it to a video file.
RecordMyDesktop is one (for X sessions, gnome based, pretty good)
For terminal only.. i cannot find one decent/easy to use/quality labeled one.
However, as mentioned above, you have the program: screen
This allowes to share a session on the terminal with others.
The viewee only has to connect to you through ssh (in case of windows: putty is a very small, no install need, client for ssh and other protocols), and then he/she can hook in on screen (with correct parameters) and view/interact LIVE with what you're doing there.
The only thing is, it won't record it to video.
Look up in google: linux screen share terminal session
or something like that (anyway the words linux, screen, share are vital keywords in your search tries).. there are a lot of tutorials/howto's about that (i saw with a few quick searches)
hope this provides a satisfying answer.