Re: confusion with terminal
The Ctrl+C thing usually helps if something is running that you want to stop, or sometimes Ctrl+Z then enter if something interactive is waiting for input. Or Ctrl+D closes a terminal.
But if you less or cat certain files that turn out to be binary, and the binary code includes something that the terminal takes to be ansi screen codes to change text or background color or the prompt, you can sometimes end up with no prompt, sometimes no echo of characters typed, or sometimes totally black on black (or white on white) invisible text. In that case you can type (blindly if you cannot read it):
hit Enter, and your screen should return to normal.
i5 650 3.2 GHz, 8 GB, nvidia GTX 550 Ti 32" 1080p | i7-4700, 8 GB, Intel HD 4600/nvidia GTX 765M 15.6" 1080p | etc.