For the ops desk these are the bookend milestones on a tracked shipment: gate-in at origin confirms the box actually made the terminal, and gate-out at destination ends terminal storage and opens the empty-return leg back to the carrier's depot. The events drive the chase: a gate-in that has not appeared as the cut-off approaches is the signal to call the haulier before the booking gets rolled, and a destination gate-out is the cue to arrange the empty return. The common confusion is with the CY cut-off: that is the deadline by which the gate-in must happen for the container to make its intended vessel, while gate-in and gate-out are the recorded events themselves.
Glossary
Gate-in / Gate-out
The paired tracking events recorded when a container passes through a terminal or depot gate: gate-in marks the container entering the facility, and gate-out marks it leaving.