Answer :

Brass is comprised of copper and zinc.
Bronze is comprised of copper and tin.
An alloy is a mixture of 2 or more metals or nonmetals or a metal and a nonmetal. Alloys are made, in order to suit the desired properties, which other metals/nonmetals don't have. Alloys are made by mixing the metal/nonmetal powders or by mixing them in molten state, etc.. 
Bronze consists of Copper & Tin
Brass consists of Copper & Zinc.
-----------------------------------------------------(HOPE THIS HELPS)--------------------------------------------