Groundspeed (GS) is the speed the aircraft is travelling over the ground in knots.
True Airspeed (TAS) is the speed the aircraft is travelling through the air in knots.
Calibrated Airspeed (CAS) is indicated airspeed corrected for instrument and position error.
Wind Velocity (WV) is the speed and direction of the wind. This does vary at different altitudes. 210/10 indicates the wind is coming from 210° at 10 knots. 5000 240/30 indicates wind at 5000 ft above mean sea level (AMSL) is coming from 240 at 30 knots.
Heading (HDG) is the direction the aircraft pointed. An aircraft won’t necessarily fly where it is heading due to wind blowing it off track (drift)
Track is the direction the aircraft is actually flying.
Drift (DR) is the difference between HDG and TMG. Drift is when an aircraft is blown off its heading or track.
Track Required (TR) is the direction the track needs to be to arrive at destination, taking into account the wind direction.
Track Made Good (TMG) is the track the aircraft is actually flying over the land after wind has already influenced the track.
Track Error (TE) is the difference between TR and TMG.
Flight Planned Track (FPT) is the original track planned for the flight.
Flight Planned Heading (FPH) is the planned heading for that sector of the flight to account for planned drift.
Track To Intercept (TTI) is the track you need to get back on planned track.
Closing Angle (CA) is the angle between the original planned track and the new TTI
True North Pole (T or °T) is the direction to the North Pole of the earth and is written as HDG (T) eg: 010T.
Magnetic North (M or °M) is the direction to the True North Pole but allowing for magnetic error and is written as HDG (M) eg: 010M
Compass North (C or °C) is the direction to the True North Pole but allowing for a compass particular magnetic error and is written as HDG (C) eg: 010C
Clock Direction is used when referencing our position relative to another aircraft we use clock positions eg: At your 3 o’clock means I am on your right.