This documentation describes how Flows can be run from REST API, listeners, or they can be scheduled.
A Flow that has a Map node as its first node, and uses a File adapter for an input, can enable that node's input to be a Watch.
Flow audits are a way to retrieve more verbose information about a flow instance.
Flow Variables are process data variables that go along with the flow execution, accessible to all nodes in the flow while it is being executed under flow executor/engine context.