explanation mark

samerrustom"explanation mark"

It is 'exclamation mark'.

samerrustomCan you explain to me when I have to put "explanation mark" please.

Well, it is wrong in your example. There is no sure way to judge; it is used when the speaker is excited. A few introductory phrases are usually followed by one, though:

Thank you for your help. I just google it and find people write it in this way "exclamation mark" not connected as your write it. Secondly, I didn't write that example, I copied it from an English learning website.
The example :
Emma: It’s a pleasure to meet you, professor. Thank you so much for helping us.

samerrustomProfessor Austin: Don’t mention it. Hopefully, I will be able to answer your questions!

Apparently, the professor is very excited to have the challenge of answering your questions.
Some people use exclamation marks far too much. There is even a name for this writer's disease -

samerrustom "exclamation mark" not connected as your write it.

That's a problem with the editor. The intention was to write two words, but the editor sometimes has trouble with boldface type.

CJ

AlpheccaStarsSome people use exclamation marks far too much.

Guilty as charged!!!

CJ

Thank you sir.
I have a question but it is not related to this subject and I hope you don't to answer it.

My question as the following:
Can I say "He is guilty"?
Can I say "He feels guilty"?

samerrustomCan I say "He is guilty"? Can I say "He feels guilty"?

Yes. Yes.

CJ