Atmos improves upon Dolby's older cinema audio offerings by providing "layers" of audio elements that (per the company) "can be positioned and moved precisely to correspond to the images onscreen." Atmos systems also rely on metadata to record how the elements behave during playback.
FastCompany's Harry McCracken, after seeing a movie clip supporting Atmos: "The versions played over the theater-grade Atmos system in Dolby's screening room were by far the gold standard. But the in-home and mobile ones sounded impressive, given the constraints they were working with."
Dolby mentioned on its FQ3 CC (transcript) Atmos commitments have been received for ~640 screens, and that the technology has been installed on over 540. ~110 of the installed screens are in China.