Sibor is like a game that banks play. In this game, the banks tell each other how much it costs for them to borrow money from each other. They do this every day so that they can make sure they are all playing fair and not cheating.
Just like how you might use different strategies when playing with different friends, sometimes the banks might use different strategies when playing this game. They might even try to guess what the other bank is going to say before they say it!
Once they all say their costs out loud, they take the average of all the costs, and that's what we call the "Sibor." This helps banks figure out what they should charge people if they want to borrow money from the bank.
So basically, Sibor is like a special game that helps banks figure out how much they should charge people to borrow money.