A file descriptor is simply an integer associated with an open file. So when you want to communicate with another program over the Internet you're gonna do it through a file descriptor, you'd better believe it. There are more, but I didn't want to scare you. I'm only going to talk about two types here. All right, already.
Stream sockets are reliable two-way connected communication streams.
They will also be error free. Any errors you do encounter are figments of your own deranged mind, and are not to be discussed here. It uses stream sockets. Also, web browsers use the HTTP protocol which uses stream sockets to get pages. TCP makes sure your data arrives sequentially and error-free.