**Definition:**
A mobile app is a software application designed to run on mobile devices such as smartphones and tablets, providing users with specific functionalities or services.

**Key ideas:**
- Mobile apps can be downloaded from app stores like Google Play or Apple App Store.
- They can serve various purposes, including gaming, education, social networking, and productivity.
- Mobile apps often use touch interfaces for easy navigation and interaction.
- They can work online or offline, depending on their design and functionality.

**Why this topic matters in this category:**
Understanding mobile apps is essential in the computer field as they represent a significant part of software development and user interaction in today's digital world.