Four Types of Feature

1. Core: Like the engine in a car, the product is meaningless without it.
2. Necessary: Like the spare wheel. Rarely used, but when needed the feature decides the success of the system.
3. Added value: Like a cup holder. Nice to have, but the product is useable without it.
4. Unique selling point: The main reason people should use your product over your competitors.

Beware category 3. Many failed features and wasted time goes into non-core, non-necessary, non-USP features in the ‘Added value’ category. Added value features often add less value than then time and effort spent creating them.