There's a lot here — but you don't need to take it all in at once. This walks you through it, one calm step at a time. Look at what interests you, skip the rest, and check things off as you go.
An “agent” is an AI worker you can hand a whole job to — not one answer at a time, but “go do this and come back when it's done.”
Many agents can be launched at once, each on a different task, all at the same time — like a full crew working every part of the ship simultaneously instead of one hand doing it all, station by station. That's why a whole fleet of sites can be built and improved in the time it used to take to do one.
One “lead” agent can captain all the others. It takes a big job, breaks it into pieces, hands each to a crew member (a “subagent”), waits for them all to finish, then pulls the work together into one result. You talk only to the captain; the captain runs the crew. You stay in command of the captain; the captain manages the rest.
The part that matters: no matter how many agents are working, a person still approves the final result before anything is published or sent.