I recommend that you actually go read some tutorial material. Classes are descriptions of "objects" which are the basis for "object oriented programming" They are also:
A way of keeping together data and the operations that are appropriate for that data (objects)
A way of thinking about programming as "stuff that 'things' can do" (methods)
A way of dividing those things into a hierarchy of ever more refined things (inheritance)
This tutorial was the first hit when I searched for introduction to object oriented programming using Google. I did not look closely at it to see if I think it is a good one, but the title sure looks right.