Pond snails are brown(red to black) and can be clear looking and round. They do not have a trap door on there foot. They breath and lay eggs under water. Eggs are clear jelly with white eggs. They only get about the size of a large pea.
Ramshorn snails are brown (mostly dark browns) and round but have more length than a pond snail. They get about the same size as a grape.
Both can eat plants, ramshorn are more likely doing this. Pond snails as said will not reproduce unless there is food for them, overfeeding, lots of algae, or soft leaf plants. Ramshorn can in some cases reproduce more than is needed.
I have ponds snails in all my tanks are very welcome to stay there. They keep the food in the bottom from rotting, eat algae. If you get to many or food amount drops or if the water gets to bad they will crawl out and look else where for food and better living area.