Screen capture allows to store what is shown on the screen. To store into a picture is usually available on every desktop environment. But when switching to an other desktop environment the used utility will probably no more be available. shutterbug is a nice featured screen capturer that comes not with many dependencies. It comes with an executable, man page, desktop file, and icon.

scrot is a command line tool. Starting scrot will capture the complete screen, scrot -s pops up a mouse cursor to select what should be captured. man scrot shows all the other options.

To store what happens on the desktop to a movie:

simplescreenrecorder is a simple gui based screen recorder that does what it is expected.

gtk-recordmydesktop or qt-recordmydesktop. The window pops up where inside the screen is seen. Inside this window the area or window to be recorded can be selected. When start recording, the window disappears. To stop the recording a button in the status bar is visible. Once captured the raw data is encoded and can be stored per default in the home directory.