Variables are a part of almost all modern programming languages. They are used to store, hold, and return data. I like to think of a variable as an envelope; just like an envelope holds its contents, a variable holds it data. Envelopes come in various shapes, sizes, and colors, each catering to a particular use. While a regular letter envelope might hold a bill or letter from a friend, a catalog envelope might contain the latest issue of your favorite magazine or a new hire package from a new job.