MentalKayse repliedHTTP = Hyper text transfer protocol. - Internet
HTML = Hyper text mark-up language - websites
URL = Universal resource locater - website address

David D repliedHTTP is how a web browser asks a web server to send it a file, and how the server does so.

A URL describes where a file is (part of the URL describes the server, part is a location on the server)

HTML is a language for describing the structure and semantics of text, and its relationship to other URLs. It is used to write webpages.

Le Fallen repliedno1's answer above is completely correct... except that the ".ext" (the extension) does not actually define a type of file. It is part of the filename and has no special properties at all. It is merely a convention by which humans (and some computer programs) try to identify a files' type or contents. This is a small but important point.

no1 repliedhttp: hyper-text transfer protocol. rides on top of tcp/ip, describes how to transact hyper-text documents.

html: hyper-text mark-up language. a markup language for hyper-text documents.

URL: uniform resource locator. a way to identify where and how to access documents on a network.

e.g. ftp://machine.domain:8080/rootdir/subdir...

the file named "file.ext" is of file type "ext" is accessible via "ftp" on "machine" at "domain" via port "8080" in the directory "/rootdir/subdir."