rf transmitter and receiver

friends we are using ht12d decoder & ht12e encoder in rf transmitter and receiver .
what is the use of address pins a0 to a7 ?
if they different for encoder and decoder means what will happen ?

check the datasheet. very first page, under "general description" says:

"For proper operation, a pair of encoder/decoder with the same number of addresses and data format should be chosen."