Simple definition
An OSPF stub area limits external route advertisements and commonly uses a default route from an area border router.
Purpose and use
An OSPF stub area reduces external routing information distributed within part of a routing domain.
How does it work?
In OSPFv2 it excludes Type 5 external LSAs and relies on an ABR-provided default route for the relevant destinations.
Example and verification
If an adjacency does not form, verify that neighbors have compatible area-type configuration.
Points to watch
A standard stub area does not remove all inter-area advertisements. Vendor variants such as totally stubby add further restrictions.
In short
Route simplification must remain compatible with the area's reachability and redistribution requirements.