You can put this solution on YOUR website! Sets are collections of elements.
Some sets have lots of elements like the set of all numbers greater than 2.
Some sets have no elements in them like the set of all basketball players taller than 10 feet tall, that's called the empty set.
Some have a finite number of elements, like the set of positive integers less than 2 which only contains the number 1 or the Latin alphabet with 26 elements starting with a and ending with z.