Emacs key bindings change in terminal emulator

Question

I notice that some Emacs key bindings change in terminal emulator (xfce4-terminal).

For example: M-SPC under TTY sets the mark, but in

Answer 1

It's not an Emacs problem so much as a terminal problem. Terminal emulators can be limited in the control and escape sequences they can send, so it's probably the case that the emulators you cited are swallowing your special characters before they even reach Emacs. Try hitting C-h l (or M-x view-lossage) to see if your key combinations are arriving in Emacs.

In addition to the answer that Legoscia cited, also check out this thread and this thread.

Unless you have a strong reason to stay in a terminal, you might consider running the GUI version and then running one of the various shells within it (eg, shell, eshell, ansi-term).