Are wedding gifts expected, and is it rude not to give one?

🪐 E.T 🪐

My new boss has invited me to his wedding, and I’ve literally never been to one in my life. It’s going to be a very small wedding, at his house, casual dress code if that makes a difference?

Are weddings gifts expected, even when they’re not asked for? And is it rude not to give one? What do you even give as a wedding gift?