<p>What is the difference between an OSPF LSA 4 and OSPF LSA 5? Both are sent from an ASBR but I am not sure what makes them different.</p>
LSA type 4 are specialized summary LSAs that advertise ASBR nodes.
LSA type 4 are not domain wide so they are regenerated by ABRs.
There is a chance that even the first LSA type 4 is generated by the ABR between area 0 and the area where the ASBR node is connected as a reaction to a setting in the ASBR Router LSA header (E bit but I didn't check) that tells it is an ASBR node.
For sure they are regenerated by ABRs at area boundaries.
In short, LSA type 4 tell what nodes are ASBR in an OSPF domain and provide routing information (path cost) to reach them using the OSPF inter-area methods.
An LSA type 5 is originated by an ASBR node and contain an IP prefix that is injected into the OSPF domain.
LSA type 5 are domain wide: they travel untouched through area 0 and all non stub areas.
LSA type 5 cannot be filtered like inter-area routes you can choice between accepting all of them or blocking all of them from entering a specific area (using the various stub concepts).
Hope to help