What is "Piece of my Heart"in relation to the Beatles?

by Roger Chafe
(St,John's, Newfoundland, Canada)

I have an Abbey Road gold 8 track award. It was awarded to "Piece of my Heart". Inscribed on the bottom of the award is "PIECE OF MY HEART" YOUR NUMBER ONE AND WITHOUT YOU WE WOULD NOT BE NUMBER ONE
I would like to know what "piece of my heart" is, and what the relationship is with the Beatles.