hptaccv, FPA=Flight Path Angle
You can have flight director on in one of 2 modes.
1. Heading & Vertical Speed
2. Track & Flight Path Vector
Or you can switch FD off and have the "bird" (FPA) displayed, as well as still having your black dot representing aircraft attitude. The beauty of FPA is that you see your angle of dangle rather than attitude which as you know changes with power, configuration etc. This way you can fly a constant angle descent without reliance on external aids.
This site will give you in depth explanation and pretty pics if you want to see what I mean.
http://www.meriweather.com/fd/fd.html