What are Actions? How are they counted?

What are Actions?

An Action is something you want to perform in one of your apps. For example, creating a new contact in your CRM or sending an email. 
In a Bot, everything defined after the Trigger Event is an action.

How are Actions counted?

If you have a Bot like the one below:
Triggers on New Row in Google Sheet, wait for 5mins and sends an email - this Bot has 2 Actions.

It accounts for 2 Actions each time it is run i.e, if this Bot runs 10 times in a billing cycle, it accounts for 20 Actions in your action quota.