The Terminal doesn't hide files at all. If you do a listing (ls) it'll show all files, including the hidden ones. ls -a to also show things like . and ..
If you mean to reveal the hidden files for the Finder, well, @MacDawg also revealed an easier method, but, if you wish to do it via the shell, it's chmod unhidden if I remember correctly. Check the man page for chmod if it's wrong, cause it's something like that. – If the file you want to see starts with a . that's another way of hiding it, so to unhide that, just rename it to something that doesn't have a . in front of it.
I should mention that unlike the other responses, my method is on a per file basis