Why is League of Legends so laggy?

My FPS or the thing on the top right, I forgot what it's called lmao, is pretty low (lower than 100) and I associate that with lag because when it's high I lag a lot. But for some reason even when it's low it's not laggy to the point where it is when it's high, but it has small choppy lags in between each step :/ idk how to fix it. And I'm sorry I feel like I made no sense while writing this lmfao.