Can someone explain the ticketing system like I am 5?

I have been to many anime and pop culture conventions and have never worked with this ticketing wishlist system.

The gaming conventions i have attended are on the smaller side, and all of the tickets are either run through Warhorn or tabletop.events, and you just sign up (and they are free unless they are VIP events).

I have never been to a panel/event that was a paid ticket. Do you have to pay to attend everything at GenCon?

If so what does your attendant badge actually pay for?

Can I just walk into a panel that is ongoing or about to start if there are seats available?

(editted to add follow up question)