HTML (HyperText Markup Language) is not a protocol, but a markup language. It describes your content.
Http (HyperText Transfer Protocol) is a protocol, it is one of the most well known and much used protocols on the internet, with https being the secure variant of it.
Other often used protocols on the internet are:
FTP (File Transfer Protocol): often used to transfer files from one server to another, or from a client to a server, or other way around.
SMTP (Simple Mail Transfer Protocol): a much used email protocol.
And there are plenty of others...