Tokens can be understood as a placeholder that will be filled in at the time an automation runs with actual data. The Transform step heavily relies on tokens to run an automation. 

It is important to use the correct token in order to pass through or have the automation understand the data from the action. 

When clicking on the {+} Insert or {+} button, you can search through numerous tokens that are available for the previous trigger or action. 

You will also notice that you will see examples of each token on the right hand side.