The Institute of Electrical and Electronics Engineers defines the term feature in IEEE 829 as "A distinguishing characteristic of a software item (e.g., performance, portability, or functionality)."
Feature-rich
A system is said to be feature-rich when it has many options and functional capabilities available to the user. Progressive disclosure is a technique applied to reduce the potential confusion caused by displaying a wealth of features at once.
Sometimes if a piece of software is very feature-rich, that can be seen as a bad thing - see feature creep and software bloat.
References
Software feature Wikipedia(Text) CC BY-SA