after some googling,
depend on the "shell" you are using.
.bashrc & .profile correspond to bash
.login & .cshrc correspond to csh
bashrc and cshrc are parsed everytime a user opens up a
new shell of the corresponding type. profile and login are parsed only if
the shell is being opened because someone's logging in. So, if you modify
the PATH in profile, for example, don't expect the change to be evident when
opening an xterm. For this reason, you'll probably want to make most changes
to the bashrc or cshrc files.