Bi party has only two parties but multi parties has many parties .i n democracy v find multi party . mostly in capitalism v find bi party . bi parties r due to he opposition and suppression .though many parties arose they were suppressed . muti party shows complete freedom of expression and speech. it gives people may options to choose. 
In bi party system system there will be only 2 party
in multiparty there will be many parties

in multiparty the people have more choice in the election
in bi party people should choose any one of the two

bi party eg- USA, England
multiparty eg India

multiparty system leads to political instability
bi party system do not cause much political instability

i multiparty system the will be coalition govt which may led to riot between parties
there is no such thing in bi party