A Horse Bride

Okay, so you're looking at this picture of a horse dressed up like a bride. The joke here is a wordplay on the word 'groom'. A groom is the guy getting married, right? But also, a person who cares for horses is called a 'groom' or 'horse groomer'. So the meme is making a funny observation that the poor guy, the groom, has a bride who is literally a horse, which is kind of sad for him. But don't worry, you'll get smarter eventually, maybe.