An OSPF Stub area is used to limit the types of LSA’s allowed to enter an area.

The types are

Intra area routes – LSA types 1 & 2

Inter area routes – LSA types 3 & 4

External routes – LSA type 5

NSSA external routes – LSA type 7

There is a great post here by packet life

http://packetlife.net/blog/2008/jun/24/ospf-area-types/

More Info

LSA Type 1 – Router – contains router links and state and is flooded into the area of origin

LSA Type 2 – Network – generated by DR – lists all attached routers – flooded into the area of origin.

LSA Type 3 – Network Summary – generated by ABR’s sent into an area to advertise prefixes to other areas – flooded throughout the Autonomous System.

LSA Type 4 – ASBR Summary – generated by ABR’s – advertises the ASBR – flooded throughout the Autonomous System

LSA Type 5 – AS External - generated by ASBR – advertises external destination – flooded throughout the Autonomous System

LSA Type 7 – NSSA External – generated by the ASBR in a not so stubby area – advertises external destination.