Each individual channel (call) in FreeSWITCH has a number of associated characteristics and values, known as "channel variables".
You use variables to get informations about the channel internals and to control the channel behavior.
Some of channel variables are assigned from the inception of the channel. Some of them change value during the life of the channel. Some variables are read-only. Some channel variables are writable, this means we can alter their value. You can (and often do) create variables in a channel, via dialplan or scripting. Specific channel variables modify the behavior of the channel, and you can take control of it by writing ("set") a variable value.
There are an incredible number of channels variables ...
