Apple Cocoa is a software framework used to develop applications for macOS, iOS, iPadOS, watchOS, and tvOS. It provides a set of tools, libraries, and APIs to developers for creating native applications using the Objective-C, Swift, or C programming language. With Apple Cocoa, developers can create applications with advanced features, such as multimedia capabilities, network connectivity, and security. It also makes use of the Model-View-Controller (MVC) architecture to separate data and logic from the presentation layer. Mastering Apple Cocoa requires a strong understanding of object-oriented programming, the Apple development ecosystem, and the Cocoa frameworks.