Conditional Processing or Execution Conditions gives you the power to decide if a particular action on the database will be performed or not when the workflow is triggered by the incoming event. This is akin to the ability to apply 'if-then-else' logic to the execution of an action based on the value of the attribute from the trigger event of the workflow.
Think of Conditional Processing as an equivalent of 'if-then-else', as decision diamond in the flow chart, or the Conditional Branching in BPEL (Business Process Execution Language).
You can add conditional processing to any action in your workflow and decide which actions should be performed in response to a particular trigger event identified by its characteristics or the data attributes. You can apply complex logic using AND, OR, and grouping of such conditions. Each of the conditions supports different operators based on the event data types like a string, number, boolean, etc. Read here to find more about Conditional Processing.
At the time of defining action if you want to perform the action depending on some criteria passed for trigger then you can use conditional processing. For example in figure 1 below, Tableau action will be carried out if the message received on Microsoft Teams channel does not contain an attachment.