What is the difference between type L and type M copper pipe

I'm planning on replacing 1/2" supply lines with 3/4" supply lines for a shower remodel.

I was wondering what's the difference between type L and type M copper pipe and what type is recommended for hot and cold water supplies?

Would there be any benefit in using PAX vs Copper? I don't know if PAX can be used in NJ.

Sorry for the fat fingering of the title, It should read "What's the difference between type L and type M"

It is the wall thickness. Most of the towns I work in want Type L copper.