1 Step 2 Step

Liam's house has a staircase with $12$ steps. He can go down the steps one at a time or two at a time.
For example: He could go down $1$ step, then $1$ step, then $2$ steps, then $2$, $2$, $1$, $1$, $1$, $1$.

In how many different ways can Liam go down the $12$ steps, taking one or two steps at a time?

A poster of this problem is available here.