What’s “briefing” in the checklist?
I have pss, and when I have the APP configured in the mcdu (on the perf button), and I active this app, the aircraft fly at very low speed, and sometimes, its going with 20º pitch up. After this, I extend the Flap1, and the speed decrease, and I extend flap2.
In this moment, the aircraft speed decrease to de minimum speed, and the plane goes on at 20º pitch up, and sometimes the aircraft begin to stall. I think I’m doing something wrong.
Briefing is done by the pilot flying the approach to the rest of the crew so that everyone is on the same page and may catch any mistakes the pilot makes before he/she makes them.
As far as flying the approach with APP, you need to look at the indicated airspeed you have set as well as the altitude that is dialed in as well. Some APP's won't work in approach mode unless you have the airport elevation in it.
Just to add a briefing will also be done prior to departure. PF will notify PNF of their intentions should there be failures before v1, after v1 etc as well as talking through the SID if there is one.