Well for starters, there are games that only the main Switch can play. The Lite version can only play some of them.
Then there's the fact that the joycons are attached to the Lite version, and can't be taken off. I THINK you can still use wireless controllers for it, tho. That's good if you still wanna use motion controls. But people say it has the drifitng issue like the joycons in general, which is bad cuz you can't change them. But maybe using the wireless controllers will be fine.
Unlike the main Switch, the Switch Lite can't be docked, so no playing games on TV. o/
I believe you can still play with other normal Switch users on some games, so that's a plus.
I think that's all the differences, to my understanding. But someone else may have more to say. o/