Schröder–Bernstein theorem
The Schröder-Bernstein theorem is like sharing candy with your friend. If you both have some candies, but maybe your friend has more candies than you, you can still share them equally.
In math, it means that if there are two sets of things, let's call them set A and set B, and we can find a way to match every thing in set A with something in set B, and every thing in set B with something in set A, then we can say that set A and set B have the same number of things.
This is really useful because sometimes we might know that there are more things in set A than in set B, but if we can still match every thing in set A with something in set B and vice versa, then we can say that the two sets have the same size.
Just like sharing candy equally with your friend, the Schröder-Bernstein theorem lets us compare sets of things even if they might not have the same number of things at first glance.
In math, it means that if there are two sets of things, let's call them set A and set B, and we can find a way to match every thing in set A with something in set B, and every thing in set B with something in set A, then we can say that set A and set B have the same number of things.
This is really useful because sometimes we might know that there are more things in set A than in set B, but if we can still match every thing in set A with something in set B and vice versa, then we can say that the two sets have the same size.
Just like sharing candy equally with your friend, the Schröder-Bernstein theorem lets us compare sets of things even if they might not have the same number of things at first glance.