Sieve

Okay, imagine you have a big bucket of sand and you want to find all the pretty rocks in it. But there are also lots of other things like leaves and twigs that you don't want in your collection of pretty rocks.

A sieve is like a special tool that helps you sift through the sand to find only the pretty rocks. You pour the sand into the sieve, then shake it around until all the small rocks and debris fall through the tiny holes in the sieve, but the bigger pretty rocks stay in the sieve.

Sieve is also used in math for finding prime numbers. Just like you sift through sand to find only the pretty rocks, a sieve in math helps you find only the prime numbers in a list of numbers. It works by crossing out all the numbers that are not prime and leaving only the prime numbers in the list.