An app store is a digital distribution platform where users can browse, download and purchase mobile applications or software. It's an online marketplace that provides access to various apps for different operating systems such as iOS (Apple), Android, Windows etc. The term 'app store' usually refers specifically to the official stores operated by Apple (iTunes App Store) and Google (Google Play Store). These app stores act as a centralized platform where developers can submit their applications for review and eventual publication, while users can easily find new apps, update existing ones, and make purchases within the store.