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.

https://en.bitcoin.it/wiki/Bitcoin-Qt
https://bitcoinhelp.net/know/how-to-get-started
https://en.bitcoin.it/wiki/Thin_Client_Security

And on who "updates and regulates" the system:
https://bitcoin.org/en/development

It's an open source project, and here you can see the work various people are doing on it:
https://github.com/bitcoin/bitcoin/commits/master

Rather, the average user should not feel guilty about not using it, but they are quite welcome to use it if they really want.

Yes. By all means try it out.

Brilliant answer, if I could rate it 5 stars xDan I would!