Use of possessives

[Zein]

Hello everybody,

I'm not sure about the use of the possessives in some cases. Maybe someone could help me.
For example, why is it "esl lessons" and not "esl's lessons"?
Maybe someone could explain also if there is any difference between i.e. "Tag reply" and "Tag's reply".

Thank you very much!
Vinicius

PS: sorry if I made some mistakes by writing.

[Michauek]

I think that the crucial difference is that you should distinguish it between Possessives and Adjevtives.
Possesives refers to someone's possesion(also things, as e.g."The shine of the moon") and Adjectives refer strictly to a noun.
"Mikel's esl lessons" as a possesive noun.
"Esl lessons" as an adjective

I think that's the point. If I'm wrong, please correct me.
_________________
absens carens
Michal. I'm an english student

[Zein]

I think that is the point too! You are right.
But I think, I could say the both "tag reply" or "tag's reply", couldn't I?

Thanks