What is the term used to describe the capability of software to help users understand its suitability and usage for specific tasks?

The term that best describes the capability of software to help users understand its suitability and usage for specific tasks is "usability." Usability refers to how easy and intuitive the software is for users to interact with, which encompasses not only the effectiveness of performing tasks but also how well users can comprehend how to use the software.

Understandability is a key aspect of usability, but it specifically focuses on the clarity of the content and the ease with which information can be grasped by users. While accessibility addresses how individuals with various disabilities can use software, functionality relates to the range of operations that are possible within the system.

Thus, usability is the overarching term that includes understandability as well as other factors, making it the most appropriate choice in the context of assessing software in terms of helping users effectively understand its usage for specific tasks.