OSPF uses LSAs or Link state Advertisements to share information of each network and populate the LSDB (Link State Database). The main LSA types are :
LSA Type 1 (Router LSA):generated by each router for each area it is located.
LSA Type 2 (Network LSA): generated by DR , link-state ID will be the interface IP address of the DR.
LSA Type 3 (Summary LSA): generated by ABR’s and flooded into other areas throughout the Autonomous System.
LSA Type 4 (ASBR Summary LSA): generated by ABR’s. To find the ASBR by other routers, ABR will generate a summary ASBR LSA including the router ID of the ASBR in the link-state ID field.
LSA Type 5 (Autonomous System External LSA): generated by ASBR and contains routes to networks that are external to current AS.
LSA Type 6 (Multicast OSPF LSA): not supported and not used(Used only for multicast applications).
LSA Type 7 (NSSA External LSA): generated by the ASBR in a not so stubby area.
LSA Type 8 (External attributes LSA for BGP): Used to work with BGP.
LSA Type 9,10,11 (Opaque LSAs)
Below table summarizes OSPF LSA Types –
Related – OSPF CHEATSHEET