If you glare at someone, you look at them with an angry expression on your face.

A glare is an angry, hard, and unfriendly look.

If the sun or a light glares, it shines with a very bright light which is difficult to look at.

Glare is very bright light that is difficult to look at.

If someone is in the glare of publicity or public attention, they are constantly being watched and talked about by a lot of people.