What is the difference between iPad Pro and iPad Air?

You can directly compare major features of iPad models here:

iPad - Compare Models - Apple (UK)

The iPad Pro models represent cutting edge performance and features. The iPad Air4 preserves the high CPU/GPU performance of the Pro models, but lacks many features - such as FaceID, larger are brighter Promotion (600 NITS/120Hz) display, orientation adaptive four-speaker array, Camera array with LiDAR sensor etc.

You can compare iPad models at https://www.apple.com/ipad/compare/ here you can compare

Compare the models specs using this link:--> iPad - Compare Models - Apple

Regards

Giulio