You’ve already gotten great answers on what Wayland is, but as far as who should care:
Mainly developers and users with niche workflows. People with NVIDIA cards should care a little as initially NVIDIA did not support Wayland, but NVIDIA drivers are catching up so this should continue to improve. Most users should just switch when their DE switches.
Oh God. For anyone thinking of doing this in the future, do not play with deer. If deer get scared, they will trample you. It’s all fun and games until a 100 lb animal starts stomping your child into the ground. Even a fawn that size could cause some serious injury to that child.