Free egress means a person can always leave a controlled door without a credential or special knowledge, usually by turning a lever or pushing a bar. Electronic locks must release for exit while keeping the outside controlled, which is why request-to-exit sensors, exit devices and fail-safe hardware are part of the design.
An access controlled door is half a security device and half an escape route. Free egress is the requirement that keeps the second half working.
Egress versus entry
The outside face needs a credential; the inside face needs a simple action. Mixing the two is where installations go wrong, such as a reader added to the inside of a door that staff then prop open. The exit side should be obvious, mechanical where possible and free of tokens.
Request-to-exit and safe release
A request-to-exit sensor or a push button tells the controller that someone is leaving and suppresses the forced-door alarm. Where a door must delay release, code limits the delay and requires an alarm and a release. Test exit with power on and off, and label the release clearly.