List Categories Only

I want to list just the Link Categories and when you click on the Category name it takes you to a page that shows all links for that Category.

This is for a School site so I want to list external resource links by Grade

I want to show

Grade 1
Grade 2
Grade 3

and so on

When they click Grade 3, it goes to a page showing the:

Link Category Name
Link Category Description
then the list of Links