Answer:
An alloy is a metal that is composed of two or more different elements. For example, Brass is Copper that has been alloyed with Zinc (meaning it has has some Zinc added to it). Stainless Steel is Iron that has been alloyed with Chromium, and often Nickel.
Alloys all have different properties depending on the different elements they are composed of, and how much of each element is present. An alloy like Stainless Steel is designed for corrosion resistance, whereas an alloy like Inconel (made from Nickel, Chromium, and small amounts of several other elements) is designed to be able to operate at high temperatures.
One property that almost all alloys have is that their melting point is lower than the pure form of their base metal. For example, Stainless Steel has a melting point that is lower than pure iron, and Brass has a melting point lower than pure copper.