Displacement reactions:
it is the type of reaction in which reaction starts with the help of two compounds,,, but in the product the reactant that was initially with 1st compound joins with the 2nd compound..
A+BC⇒AC+B
example:
Fe+CuSO4⇒Cu+FeSO4
Double displacement reactions:
while it is the type of reaction in which one product is obtained parts of both reacting compounds interchange with each other..
AB+CD⇒AD+BC
example:
AgNO3+NaCl⇒AgCl+NaNO3.....:)