Confusing instructions on Campaign Modal choices

If you are going to create a new campaign that will be sent to segments, the user is offered the option of: Decision. Action. Condition.

The Decision options states: “A decision is made when a contact decides to take action or not (e.g. opened an email).”

That would be interpreted to mean that a recipient, for example, opens an email and as a result, something would happen in Mautic or a decision tree would exist. Since the explanation on the Decision choice states e.g. “opened an email” one would naturally expect to find that option available in the list of decision pull down choices, but it’s not there.

So this is confusing.

Can a user actually trigger an event upon a contact opening an email as stated in the help text of this choice (decision) and if so, why isn’t it listed in the choices?