If you do the dot and then space, and then the file name (with path unless it's in $PATH), then it will execute in the current shell. That means you can set your prompt or whatnot and it will affect your current shell.
. /path/to/script
I use this to do things like set my prompt and whatnot. It's basically shorthand for calling "source".
The technical details are that it does not fork a new process and run the program in the new shell, but will run it in the current process space. Instead of a fork and exec, it just issues an exec.
The "." in ./script is shorthand for your current directory. That's why when you do an "ls -al" you see "." and "..". The ".." is parent directory, so it's a way of saying "back up a directory". If you're in /home/name/blah/yadda, and you want to execute /home/name/lala, then issue "../../lala/script"
Anyway, just giving you more info to confuse you :)
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James McPhee
jmcphe@gmail.com