What does the ‘brief’ in briefing stand for?

Today I got to go to work to brief an incoming team about airlift. The first thing I learned the hard way is that on Saturdays my usual door in the Embassy is locked. The other thing is that the bosses must not have anything to do on a Saturday because they went on and on and on. I got home eventually and walked to the Andino to eat lunch with Chuck before the daily torrential downpour.