Original: The Hershey - Chase experiments were a series of experiments conducted in 1952 by Alfred Hershey and Martha Chase, confirming that DNA was the genetic material, which had first been demonstrated in the 1944 Avery - MacLeod - McCarty experiment.
Simplified: These experiments were to make sure that DNA was the genetic material which had first been discovered in the 1944 Avery-MacLeod-McCarty experiment.