An SDK (Software Development Kit) is a collection of tools, libraries, and documentation that developers use to create applications for specific platforms. Its primary function is to simplify the software development process by providing pre-built components, enabling developers to focus on building features without starting from scratch. SDKs typically include APIs (Application Programming Interfaces), which facilitate communication between different software components, thus enhancing functionality and ensuring compatibility. By using an SDK, developers can significantly reduce development time and improve the overall quality of their software.