How does my router gets a public ipadress and connects to the internet?

I'm really a noob in networking, just started learning a bit for fun and I didn't find a lot of stuff about it so I thought I just ask here hope that's okay lol

I read on the Internet that my router basically just connects to another "big router" which uses dhcp to give away ip's, but how does my router connect to this "big router". Like my router is just plugged in into an electrical outlet, how does it get a connection with something and then an IP. I can't see other networks than the one from my router if I scan for networks on for example my phone. So how does my router gets a connection with this "big router".