A feed is a link that a client's website or job board reads to list the vacancies the client publishes on its careers site. A company has one feed at most.
The link holds the feed's client id and a secret key, so whoever has the link can read the feed. This console never shows the key: Copy link puts the whole link on your clipboard, to send to the client through the usual channel.
Rotate key gives the feed a new link and stops the old one at once. Use it when a link has reached the wrong people.
Internal vacancies, when ticked, adds a second version of the same link that lists the vacancies on the client's intranet and records its applicants as internal.
Everything done here, reading and copying included, is recorded with your name in Audit.