Canon entered the mirrorless market in the summer of 2012, several years after some competitors. Unfortunately, this didn’t go very well for them in the US and European markets, and Canon withdrew importing new EOS M gear into the US in 2013 as a result. They reversed this position in 2015 and now again bring mirrorless into the US and European markets.
Canon uses the same crop sensor size for the EOS M as they do for the Kiss/Rebel DSLRs (APS-C), and thus performance and to some degree, features, are very similar to the Canon DSLRs.
Four generations of EOS M exist (M, M2, M10/M3, and M5/M6). Here are the data pages for each:
Available Canon EOS M Lenses