A proportion states that two ratios or rates are equal. It is an equation. You can solve them. In order for two ratio or rates to be a proportion they must be equivalent.
Proportions are very useful in real life. They can be used to find distances and heights of objects. As humans our bodies are proportionate. They are used daily in the culinary world when a recipe needs to be reduced or doubled. Take for example, you are throwing a party and have decided to make bbq chicken. It is recommended that 1/2 lb to 3/4 lb be made per person. You have decided to go with 3/4 lb per person. There are 38 people coming to the party. You can use a proportion to find out how many pounds of chicken you will need to feed everyone at the party.
How do proportions apply to triangles and other figures? How are we going to be using proportions? In the next module, 6.1 - Similar Polygons, you will learn how proportions apply to similarity figures.