What is the difference between MIME, Internet media type and HTTP?

Question

From what I have read, MIME is something that is used for encoding e-mails.

Then there's this thing called Internet media types.
We have Internet media types like text/plain, application/json, image/png etc.

Then we have HTTP protocol with its Content-Type headers, examples of valid headers include:

Content-Type: text/plain
Content-Type: text/plain; charset=utf-8
Content-Type: multipart/mixed; boundary=blah (source)

So is string such as "text/plain; charset=utf-8" an expression bound to HTTP protocol, MIME standard or a completely valid Internet media type?

What exactly are the relations between each of these protocols?

Answer 1

"Internet Media Type" is the correct term for "MIME type".

"Content-Type" is the name of the HTTP (and mail) header field that carries the media type in the field value.