What is lightning network?

Hi i am new to bitcoin and don't know much but I am trying to learn more. I see people talking about lightning network a lot now so i was wondering what it exactly is and how it is different from the normal btc. I tried googling but the terms are somewhat difficult for me to understand as a noob so i would be grateful if someone could make it simple for me to understand. From what i see, lightning wallets are separate from normal btc wallets. So i was wondering if i receive btc through lightning, can i spend it as normal btc and send it to others? Or does it have to be only through lightning? Thanks in advance.