Adobe ExtendScript is a JavaScript-based programming language used to create scripts for automating tasks and workflows in Adobe applications. Scripts developed with ExtendScript can access and manipulate objects within the host application's scripting model, allowing users to perform complex operations or customize functionality more efficiently than through manual methods. The language supports conditional logic, loops, functions, and error handling capabilities, as well as the ability to extend the core features of Creative Cloud applications such as Photoshop, Illustrator, InDesign, and After Effects.