A uniform is a special set of clothes which some people, for example soldiers or the police, wear to work in and which some children wear at school.

You can refer to the particular style of clothing which a group of people wear to show they belong to a group or a movement as their uniform.

If something is uniform, it does not vary, but is even and regular throughout.

If you describe a number of things as uniform, you mean that they are all the same.