Benjamin Franklin is probably most famous for flying kites in thunderstorms. In the mid-1700s there were three different phenomenon that had similar effects. You could draw sparks with frictional or static electricity. Lightning appeared to be a giant spark, and electric eels could cause shocks like static electricity. But no one knew if these three had the same or different causes. Franklin touched a Leyden jar to a key tied to the string of his kite. When sparks jumped from the cloud to the kite, the charges went down the string and charged the Leyden jar. Thus Franklin showed that lightning and frictional electricity were the same.
Benjamin Franklin did not discover electricity, but he did show that lightning and frictional electricity were the same thing with his famous kite experiment involving a key and a Leyden jar.