CFM at a given pressure is the number that decides whether a compressor can actually run an air tool, and it is listed on both. A tool rated at 4 CFM will not perform on a compressor that delivers 2.
Impact wrenches state maximum torque and the drive size. Compressors state tank size, motor horsepower and duty cycle. Coupler styles (industrial, automotive, ARO, V-style) are not interchangeable and the style is stated on each fitting.
