Never jailbroken a PS3 before, any help?

Hello everyone! I have never thought of jailbreaking my PS3 until today, when I started Googeling about it. But when searching through the links a lot of strange jailbreak terms come up that I don't understand. And it also isn't clear for me if I can actually jailbreak my PS3 or not.

I have got a PS3 Slim, 320GB and the back sticker says CECH-2504B. I think it had firmware 3.75 when I bought it new in the shop. So according to some topics on this forum I need (correct me if I'm wrong) to be on firmware 3.55 to be able to jailbreak my PS3 so I can run backups and such, am I right? Well.. I am on the latest firmware right now, 4.40 I believe. So is there a way for me to downgrade to the jailbreakable firmwares (preferably without any hardware).

What do all the shortcuts and other terms mean? What is a homebrew? What is Cex>Dex, NAND? What are the pros and cons of the different custom firmwares? Think of me as someone who has NEVER seen any of these seemingly common PS3 jailbreak terms when you formulate your answer or I might not get it haha

What do I have to do and know to be able to jailbreak my PS3 Slim 320GB CECH-2504B on the latest official firmware 4.40 so that I can run game backups and such?

Thanks for reading and/or replying!