What is a shell extension?

A shell extension is a software component that extends the capabilities of a file manager or operating system shell, such as Windows Explorer. It allows developers to add custom functionality, such as context menus, toolbars, or property sheets, enhancing user interaction with files and folders. Shell extensions are typically implemented as Dynamic Link Libraries (DLLs) and can provide features like previewing file types, integrating with other applications, or adding new commands to the right-click context menu.