What is the Difference Between Similar But Different Things, Terms, and Objects

What is the Difference between m16, ar-15, sks, m4, ak-47 and ak-74

The use of guns is not new, as this is a very old invention. However, many remarkable changes have been brought about in the model, designs and functions of guns. On behalf of such designs and different ranges, guns can be categorized in different names. Some famous guns are like m16, ar-15, sks, m4, ak-47 and ak-74.