1)Attitude Hold - holds pitch and roll
you can make adjustments (movements) while you flying without trim the aircraft just move your stick and leave it
keep in mind that is automatically disengaged when: load factor is greater than +4g and less than 0g
2)Altitude Hold - holds altitude and roll
basically what im doing is to engage first the Attitude Hold and then the Altitude Hold
is almost exactly like ALT\HDG in A-10C
keep in mind that these modes become very useful for AAR
just engage Attitude Hold and when you are exactly at the right position to connect with the Tanker engage the Altitude Hold and just play with the throttle
is also keeps a turn for you!!!!
hope that it helps a bit!!!