Process tagging allows you to assign a string to processes to identify them. This is most useful for setting the version of your application that you're currently deploying. For example:

$ procodile start -t 189f7ca

Once you've set a tag, it will be assigned to all processes started while it's set. It is recommended to pass it to your start and restart commands.

It can be useful to help you identify any zombie/old processes that haven't stopped running under normal operation.