Ambivalent sexism means having mixed or contradictory feelings about women. It's like sometimes you think women are awesome and sometimes you don't like them very much.
Ambivalent sexism can come in two different forms: Hostile sexism and Benevolent sexism.
Hostile sexism is when someone is openly negative and aggressive towards women. For example, someone might say that women are weak or inferior, or they might treat women badly on purpose. That's not okay, and it's a kind of sexism that we want to get rid of.
Benevolent sexism is a bit trickier. It's when someone is really nice to women in a way that seems kind, but is actually based on old-fashioned gender stereotypes. For example, someone might say that women need to be protected, or that they're not very good at things like sports or math. These ideas might seem nice on the surface, but they're actually holding women back and limiting what they can do.
It's important to recognize when these kinds of ideas come up and speak out against them. We should all be treating everyone equally and giving them a chance to be their best selves, no matter what their gender is.