The URL for a website can tell you a lot about the purpose of a webpage.
.com = commercial site
.net =network provider
.edu =education - school or university
.mil = military website
.gov = government website
.com, .net, and .org sites are less regulated, meaning anyone can register for a website with that domain.
Note: .edu, .mil, and .gov sites are MORE REGULATED, and tend to be more reliable.