A combination is a selection of items from a larger set where the order of selection does not matter. It is used to count the number of ways to choose m elements from a total of n distinct elements.
\[ C(n, m) = \frac{n!}{m!(n - m)!}, \quad (n \geq m) \]
Where:
\[ C(5, 2) = \frac{5!}{2!(5 - 2)!} = \frac{5!}{2! \cdot 3!} = \frac{5 \cdot 4 \cdot 3 \cdot 2 \cdot 1}{2 \cdot 1 \cdot 3 \cdot 2 \cdot 1} = 10 \]
There are 10 ways to choose 2 elements from a group of 5 without considering the order.