Glossary
Shared Responsibility Model
A shared responsibility model states, explicitly, which security controls a platform provides and which ones are left to whoever builds on top of it — a cloud provider might secure the underlying infrastructure while leaving application-level access control entirely to the customer, for instance. Without that division stated clearly, both sides can end up assuming the other is handling a given control, which is exactly how gaps appear.
The model only helps if it is read and acted on, not just published. A team that never checks which controls are actually theirs to implement gets no benefit from a clearly stated division they never looked at.