I am assuming you are being asked to compute how many ways there are to choose 2 songs from a list of 7. We'll call this number \(\displaystyle N\). For the first song, we have 7 choices and for the second song, we have 6 choices. If the order of the two songs matters, then we take the permutations, i.e:
\(\displaystyle \displaystyle N=7\cdot6=\frac{7!}{5!}\equiv\,_7P_2\)
However, if order doesn't matter, then we have:
\(\displaystyle \displaystyle N=\frac{7\cdot6}{2}=\frac{7!}{5!(7-5)!}\equiv\,_7C_2\)