I am not sure what this Apple Music does for me. Do I really need it?

It's completely optional.

It's a subscription to have unlimited access to all the music available in Apple Music. You can listen to anything anytime, even offline. But you don't own any of the songs, you're just renting (as long as you keep paying).

Wether you choose to subscribe or not, you always have the other option to go to the iTunes Store and purchase whatever you want. Those purchased, you do own.

I hope that helps

Apple Music allows you to stream and download unlimited music for a monthly fee. If you unsubscribe any music you have downloaded will no longer be available. You do not need it, it's up to you.

Music - Apple