Subsets of Sets

What is meant by a superset of a set? 

Find the total number of subsets possible for the set $A=\left\{1,3,5,7,9,11,13,15\right\}$ .

Sets $\mathrm{B}=\left\{0,3,5,7,9\right\}; \mathrm{A}=\left\{1,3,5,7,9,11,13,15,17\right\}$

$\mathrm{B}$ is proper subsets of the set $\mathrm{A}$.

Find the number of subsets of the following set $A=\left\{1,2,3,4,5,6,7,8,9\right\}$.

If $A=\left\{a,b,c\right\},$ the number of subsets of $A$ is