is used to say that something is 'helpful', 'good to know', or 'handy' It is different from 役に立つ in that it is specifically for sharing knowledge, tips, or information.
ハワード先生の授業はためになりません。 Howard-sensei's lessons are not very helpful for getting information.
ためになる！ Thanks for sharing, that's very useful!
Youtube: Japanese ammo with Misa - ために vs ように To.../For... ためになる = useful?