MacOS Catalina, released on October 7, 2019, is the sixteenth major version of macOS, Apple's desktop operating system. It's known for several key changes, including the introduction of Sidecar, which allows users to use an iPad as a second display, and the replacement of iTunes with separate Music, Podcasts, and TV apps. Catalina also emphasizes 64-bit software, dropping support for 32-bit applications.