lens - What's the difference between Canon EF-S and EF-M?

What is the difference with Canon EF-S and EF-M lens?

Answer

The EF-M lenses are designed for the new mirrorless camera system, and mount much closer to the sensor than the EF-S lenses (which are designed for DSLRs with a mirror box).

You can use EF-S (and EF) lenses on the M system cameras using an adapter (which is just a spacer with some electrical connections to move the rear of the lens further from the sensor), but you cannot use EF-M lenses on Canon's APS-C-format DSLRs. (Unless someone makes an adapter with additional optical elements; the distance between the lens mount and the sensor would prevent anything even approaching infinity focus without additional lens elements.)