Jim is on the right track for most turboprops. Propeller blade angles are measured fore & aft of zero degrees. At zero degrees, with the aircraft not moving and the engine running, there is theoretically zero thrust. During this phase of operation, the propeller blade angle is controlled directly by the power lever (throttle). Moving the power lever forward places it in the ground idle detente and moves the propeller blade angle to (typically) about +11 degrees. Movement of the power lever to this point does not change engine or propeller RPM, just blade angle. Further movement forward of the power lever increases engine RPM and consequently propeller RPM. As prop RPM increases, governers within the propeller dome prevent the RPM from increasing beyond certain amounts (typical to manufacturer). The way the governor restricts prop RPM is to increase prop pitch further. As an example, during take off, the engine and propeller of a PW100 engine typically reach 90% torque and 1210 RPM. Once the 1210 RPM is reached, prop pitch is increased/decreased by the prop governor to maintain that RPM (if RPM decreases, prop governor increases oil pressure to reduce prop pitch; if RPM increases beyond 1210, the prop governor reduces oil pressure to the prop dome causing an increase in prop pitch).
Confused? It gets better. As stated earlier, with respect turboprops, oil pressure drives the propeller from coarse pitch to fine then reverse pitch. Feathering springs counter the oil pressure and try to drive the prop pitch to full coarse/feather pitch.
Remembering the description of "degrees" above, if zero degrees represents zero thrust at zero forward airspeed, then the same zero degrees of pitch will represent a great deal of drag if the airplane is moving forward at say 100 knots (as in landing). The position of the props at this zero degree setting is called "discing". Discing is frequently used after landing to help slow the airplane, and utilizes minimal fuel and produces the least amount of noise. The power levers usually have some kind of detente at the discing position.
To prevent the pilot from inadvertantly selecting "discing" while in flight, so too does the flight idle setting of the power levers have a detente. On some aircraft this can easily be overridden, even in flight, but it takes conscious effort, and can be very dangerous.
Not finished yet:
Once on the ground during rollout, if more stopping energy is desired from the powerplant, continuing to retard the power levers moves the prop blades into negative territory, i.e. -15 degrees (typical). At the same time, the power levers cause the engine to accelerate. More engine power + increasing large negative prop blade angles = increased reverse "thrust".
Most modern turboprops have very distinctive noises when taxiing on the ground. Most pilots use little or no braking while taxiing. Both these phenomena are directly related to the fine movements of the power levers while manoeuvring on the ground, with minute changes of the propeller pitch. The engine speed/power remains unchanged.
In closing, the range of pitch of the turboprop blade goes from (approximately) 90 degrees (feathered) back through the entire range to minus 15 degrees (full reverse pitch). Forward flight blade angles range from about 17 degrees to about 70 degrees. These measurements are all made with respect the prop installation on the engine and have no signifigance with "angle of attack".
Hope that clears up some of the mystery without producing more confusion!