An ASR (Approach Surveillance Radar) approach is a type of radar approach in which a controller provides navigational guidance in azimuth only. The pilot is furnished with headings to fly in order to align the aircraft with the extended centerline of the landing runway. Since no glide slope is provided, it is considered a non-precision approach and pilots must adhere to appropriate minimums. However, the controller will provide recommended altitudes at each mile if requested by the pilot. 

A PAR (Precision Approach Radar) approach is a type of radar approach in which a controller provides highly accurate navigational guidance in azimuth and elevation to the pilot (it is therefore a precision approach with a “verbal glide slope” provided by the controller until the aircraft reaches the published Decision Height). The controller will give trend information using statements such as “slightly above glide path,” or “well above glide path, coming down rapidly.” If the aircraft deviates too far outside prescribed safety zone limits in azimuth and/or elevation, the pilot will be directed to execute a missed approach or fly a specified course unless he has the runway environment in sight.

A No-Gyro approach is a radar approach/vector provided in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues the control instructions "Turn Right/Left," or "Stop Turn," as appropriate. All turns should be executed immediately at standard rate until on final; then one-half standard rate on final approach.