Consider the prime factorisation of 12:
$$\begin{align} 12 &= 2 \times 6 \\ &= 2 \times 2 \times 3 \end{align}$$
So $12 = 2^2 \times 3^1$.
Can you see how the table below can be used to find the six factors of 12?
$2^0$ 


$2^1$ 


$2^2$ 

The first branch gives us $2^0 \times 3^0 =1$
The second branch gives us $2^0 \times 3^1 =3$
The third branch gives us $2^1 \times 3^0 =2$
The fourth branch gives us $2^1 \times 3^1 =6$
The fifth branch gives us $2^2 \times 3^0 =4$
The sixth branch gives us $2^2 \times 3^1 =12$