Variables are used in most programming and scripting languages. In Asterisk, we can use variables to simplify our dialplan and begin to add logic to the system. A variable is simply a container that has both a name and a value. For example, we can have a variable named COUNT which has a value of three. Later on, we'll show you how to route calls based on the value of a variable. Before we do that, however, let's learn a bit more about variables. The names of variables are case-sensitive, so COUNT is different than Count and count. Any channel variables created by Asterisk will have names that are completely upper-case, but for your own channels you can name them however you would like.
In Asterisk, we have two different types of variables: channel variables and global variables.