Patronize has two very different meanings, and understanding both helps you navigate social situations and spot when someone might be treating you unfairly.

1. To treat someone as if they're less intelligent or capable than they actually are. When someone patronizes you, they talk down to you, explaining things you already understand or using an overly simple tone, as if you couldn't possibly grasp normal conversation. A teacher who assumes you can't handle challenging work might speak to you in a patronizing way, or an older sibling might use a patronizing tone when they act like every question you ask is foolish. This kind of behavior feels insulting because it shows the person doesn't respect your intelligence or abilities. The adjective patronizing describes this condescending attitude.
2. To be a regular customer at a business or to support an artist or cause. When your family patronizes the local bookstore, you shop there regularly. Museums and orchestras depend on wealthy supporters called patrons who help fund their work. Today, being a patron simply means supporting something you value, whether that's a neighborhood restaurant, a theater company, or a favorite author whose books you always buy.