I have a question

I have seen on this forum people tagging other people like in discord for example: @YourName so I would like to know if that actually tags people.

No it doesn't actually tag people but if it's on a thread that a lot of people comment on it's a handy way of letting someone know that you are answering their question, makes it easier to find a response if there's spam on the thread

So you can just say their name no need to do @

The @ isn't a character people tend to use, unless putting it before a name. And it's not the same kind of character either, thus is helpful to see more easily when / where someone replies to someone (I also do it when I just talk about someone in a reply to someone else, for the same reason).
This can also be some kind of habit, too.

I think they don't get a notification, but it would be a great feature if you could do that like in discord.

Yeah it is but it can be abused

In discord, you can block a person, so that way when he/she mentions you it doesn't actually mention you, that would be a great idea to prevent spamming.