Wikipedia
.app (gTLD)
.app is a gTLD ( generic top-level domain) in ICANN’s New gTLD Program available in the Domain Name System from late 2015.
The name "app" is a short form of the word application often used in IT-sector. This domain name is to be used by developer companies, professionals and enthusiast developers and entrepreneurs applications, app-support services or other useful related products and tools.