Automated business process that can execute logic, interact with SFDC database, call Apex classes, and collect data from users
Uses connectors, elements, and resources
Can update, create, get, delete records
Can send core actions like emails, submit for approval, create chatter post, etc.
Use when functionality cannot be achieve through process builder or when requirement is too complex for it
Can perform most core actions like submit for approval, send email, create chatter post, etc.