Difference among Point to Point,Broadcast and Non-broadcast multiaccess networks

Point-to-point:
                      A point-to-point network joins a single pair of routers. A T1 serial line configured with a link-layer protocol such as PPP or High-Level Data Link Control (HDLC) is an example of a point-to-point network.
Broadcast:
                     A multiaccess broadcast network, such as Ethernet.
Nonbroadcast multiaccess (NBMA):
                     A network that interconnects more than two routers but that has no broadcast capability. Frame Relay, ATM, and X.25 are examples of NBMA networks.

For Further Reading,

General, Networking