Battery Vatchmacallit

Today I replaced the battery on my 2013 Triumph Trophy. There were two wires going to each terminal, plus a plastic piece that sat on top of the battery, secured by the rubber strap. It was covered in what appeared to be dielectric grease, and a plastic part slid into another plastic part that was connected to what appeared to be a multi strand electrical cable. What in the world does that do? Thanks!