Tee channel is used to spread the message to everywhere. For example, you have message called A. You could send A to person1 to do product and person2 to do minus with tee channel.
This patterns is same concept with Linux tee command. Although linux tee command only send data to two outputs, here I implement to send data to multiple outputs. Please refer Tee Channel Example Code。
By the way, it's similar to Pub/Sub, you could check the very simple version 02-Pub/Sub in this repo.