what is the 'host' for SMTP?

[John Salerno]

If I want to write a cgi script that reads the contents of an HTML form 
and emails it to me, what would I use as the host parameter for my SMTP 
instance? The example in the docs is 'localhost', but I don't know what 
that means or refers to. I imagine I would have to use something that 
was tied to me specifically, but tied to what? My computer? My email 
address?