Read About LSA1 and LSA2
ABR(Area Border Router) sends the summary LSA type 3 on by area and rest of the OSPF AS. LSID is set to the network number, the mask is also advertised. By default OSPF doesn't summaey group of contigious networks. By default type 3 lSA is advertised into the backbone area for every subnet defined in the originating area which could cause significant flooding problems consequently should configure the manula route summary at ABR. Summary lsa are flooded only in a area but regenarated by the other ABRs and flood in other areas.