Taken from https://www.optimizely.com/uk/optimization-glossary/feature-flags/
What are Feature Flags?
Feature flags are a software development technique that turns certain functionality on and off, without deploying new code. This allows for better control and more experimentation over the full lifecycle of features.
The idea behind feature flags is to build conditional feature branches into code in order to make logic available only to certain groups of users at a time. If the flag is “on” new code is executed, if the flag is “off” the code is skipped.
Also referred to as feature toggles, feature flags are a best practice in DevOps, often occurring within distributed version control systems.