What is difference between DR and BDR in OSPF?

IN OSPF WE HAVE MANY NETWORK TYPES, FOR eg point-to-point, point-to-multipoint. broadcast and so on 

DR AND BDR BOTH ARE ELECTED IN (BROADCAST AND NONBROADCAST) MULTI ACCESS NETWORK TYPE IN OSPF . 

dr has two functions 1. generating network lsa which has information of all the routers attached to that multiaccess network .

                              2.  advertising the link-state database information to all routers in the multi-access network . 

both dr and bdr have same functionality but both are not activly doing that job at the same time. 

both listen to address 224.0.0.6 but only dr advertise lsa update to allspf router address i.e 224.0.0.5 , bdr can only do this if dr fails and it itslef become dr. 

if there is no bdr , there is not dr also as 

for eg in the eg 

r2----r1-----pc1   r2 and r1 connected to eachother via serial link and r1 is connected to pc1  via ethernet link. in this case if we configure ospf area 0 on both r2 and r1 links . we will find no lsa2 is there on r2 or r1 , and r1 is not electing and dr on link between r1 and pc1.