**Definition:**
An interface in computer science is a shared boundary across which two or more separate components of a computer system exchange information. It defines how these components interact with each other.

**Key ideas:**
- Interfaces can be user interfaces (UI) for human interaction or application programming interfaces (API) for software communication.
- They help standardize interactions, making systems easier to use and integrate.
- Interfaces can improve usability by providing clear and consistent ways for users or programs to communicate.
- They are essential for building modular systems, allowing different parts to work together smoothly.

**Why this topic matters in this category:**
Understanding interfaces is crucial for designing effective computer systems that are user-friendly and easily maintainable.