Two quantities being proportional means that they are related to each other in the same way. Say you have 1 item out of 4, and 2 items out of 8. These quantities are proportional because 2 is 1 * 2 and 8 is 4 * 2. Any simple fraction can have a multitude of proportional fractions. In the case of fractions, they are not only proportional, they are equal. Proportions are used in a variety of ways to solve equations. Percentages, fractions, and many other things.