Functionality refers to:
* The ability of something to work effectively and fulfill its intended purpose. For example, the functionality of a smartphone includes making calls, sending messages, accessing the internet, and running apps.
* The features and capabilities of a product or system. For example, a website's functionality might include the ability to search for information, create an account, and make purchases.
Therefore, if you meant "functionality," it refers to how well something performs its intended tasks.