The big difference with Dolby Atmos and DTS:X, compared to older audio formats, is that they go beyond the traditional 5.1/7.1 speaker philosophy. Instead of sending sound to discrete channels, they're "object-based" formats that expand the sound field across all of your speakers. Notably, that includes speakers either mounted above you or with upward-firing capabilities that bounce sound off of your ceiling.
While they're both niche formats, there are plenty of Blu-ray titles on the market that support Atmos, like Mad Max: Fury Road, Jupiter Ascending and Game of Thrones. That codec should also pair nicely with the Xbox One S's 4K Blu-ray drive, as most UHD titles also include Atmos support. And of course, it'll likely be something the upcoming Project Scorpio supports as well.