Question: what is the difference between an ospf neighbor and an adjacent neighbor?
Answer: Your Google search keywords are ' OSPF Neighbor states'). In 2-way state, basically, when 2 routers are "Neighbors", they don't share their complete database (LSDB) with each other. They only share hello's which tells them about their existance. ... In Adjacency, the routers share their complete LSDB's with each other.