There are three main types of mobile apps including native apps, web-based mobile apps and hybrid apps. Hybrid mobile apps combine elements of native and web-based apps. Native apps include Android, Windows Phone, and iOS.
The word "app" is an abbreviation for "application." It's a piece of software that can run through a web browser or offline on your computer, and on a smartphone phone, tablet or other electronic devices, including smart TVs and smartwatches. Apps may or may not have a connection to the internet.