Alloy is the combination of elements with at least one element being a metal. This is usually done to create a stronger element. A combination of two elements is called binary alloy, and a combination of three elements is called ternary alloys.
A common example is a steel. Steel contains iron and carbon. Steel is a lot stronger than iron. Composite is made from a combination of different materials, and metals are not a necessary part of the combination. For instance, the combination of cement, sand, steel rods with water is used to form cement concrete.
The alloy and the composite are known to be highly similar to each other. The composite is made out of two or more components that will not be composed of metals. The alloy is also composed of two or more components but it should have some metal as a part of the mixture.
Take note that alloys and composites are known to have some differences depending on the type of materials that are usually placed or mixed together. Steel is an example of an alloy because it comes with some metal materials that will ensure that it will do exactly what it is supposed to do. Some of the materials retain their original properties.