An API Client is a software application or tool that enables communication between a user and an API (Application Programming Interface). It sends requests to the API and receives responses, allowing users to access and manipulate data from a server or service. This interaction is essential for integrating different software systems and services. API Clients can be found in various forms, such as libraries, command-line tools, or graphical user interfaces. They simplify the process of making API calls by handling the complexities of network communication, data formatting, and error management, making it easier for developers to work with APIs.