Cookies and Biscuits are somewhat similar however the difference between a biscuit and a cookie is that cookies are usually round and soft to chew.
While a biscuit is usually harder and can be either round or square or rectangle in shape.
In British English Biscuits refer to a small, baked, unleavened cake, which is typically crisp, flat, and sweet.
Cookies in America refers to soft and sweet flat baked goods.
Cookies mostly are soft and round and use some different ingredients while biscuits are usually harder and use different ingredients to make.
So they are almost similar but cookies and biscuits are different.