Yeah, those tiny brown ones with the long shell are malaysian trumpet snails. They're pretty cool but they do multiply fast. Speaking of those...you just reminded me that I set three baby MTS snails loose in one of my tanks a few weeks ago

I haven't seen them since but they'll prolly pop up someday.
Not all snails multiply like that. Apple snails lay eggs, as to most of the larger snails that you see. Snails like to eat veggies. I give mine mostly Kale, spinach, mustard greens and carrots. They loove spinach. They get the occasional grape or cucumber also. Snails need an average of 2.5 gallons a piece, more is better because they're pretty messy.