A quick overview of the workflow builder by default you'll be on the actions tab where you can actually build your flows.

Settings

Time window--a sending window means that the outgoing messages within your workflow can only go out during this window.
Allow Multiple --if you turn this on, it means that any single contact can go through this workflow more than once, it its off they can only go into the workflow once and the second time that a trigger tries to add them nothing will happen.
Stop on response-- if you turn this on and a contact in this workflow replies to any of the messages that have gone out or books an appointment the rest of the workflow will shut down.
Auto mark as read--normally outbound message from a workflow will show up in the recent tab of conversations.
Event start date- are great if you're running say a webinar on a future date and you want to do appointment reminders leading up to that date and time.

Status

Status tab-- shows you an overview of everybody who's been in this workflow and where they're at so we can see some of these have finished the workflow. Some of them are still at wait steps and you can which step they're at here and when the next action will happen for them.

Execution log-- this will take you to an overview of that contact since they've been added to the workflow.

History tab

This tab enable to see a complete history of every event that's fired in this workflow.

Actions

Here's where we actually build our workflows and they all start off by adding a workflow trigger.

Workflows Overview