Think about a case where you have 4 routers with a LAN, A, B, C and D. A will be the DR and B will be the BDR. In such in a situation, router C’s neighbor state per neighbor will be as follows:
A – Full
B – Full
D — TwoWay
Each non-DR/non-BDR router will be in a Full state while using DR and BDR but will be in the TwoWay state with other non-DR routers. That simply shows that the router has two-way communication achievable neighbor but has not established an entire adjacency with it, since the router will only establish adjacencies while using DR and BDR.