Okay thanks, I still don't understand but good enough for me. Lol
It's just one of many pieces of software you could use. Like if you were filesharing with bittorrent or something, there are many different softwares for that.
The Bitcoin Core is probably the most secure, as it is a "thick client", as opposed to the lighter weight "thin clients". And Bitcoin Core is the one maintained by the main (core) bitcoin developers, and forms the backbone of the network.