IAS- indicated air speed? TAS--True air speed? 
okay...so the two of us are asking...what the heck it that?
IAS - Indicated Airspeed: Airspeed that is shown on your airspeed indicator.
CAS - Calibrated Airspeed: IAS corrected for instrument error.
TAS - True Airspeed: Speed at which your aircraft moves though the air.
EAS - Equivalent Airspeed: At high speeds & altitudes IAS & CAS read incorrectly due to compression. EAS shows the airspeed as it would be at sea level.
GS - Ground Speed: Speed at which your aircraft moves over the ground.
Mach: Your speed in relation to the speed of sound at the given altitude & pressure.
Hope this helps.