Locahost.com is a redirection service for web developers and anyone else who has occasion to run a local http server.
Confused? This means either you mistyped, or whoever wrote/configured the page/site/service you just came from screwed up. It happens, don't stress it (and don't blame me.)
L O C A host. See? No 'L', so your browser kindly appended .com, and you ended up here, instead of http://localhost/ which you presumably intended.
Note: This is not localhost.com either. See? No 'L'.