It’s what the name implies. A song contest. European countries plus, randomly, Israel and Australia. ABBA famously won it back in the day. There days the counties tend to vote for countries they like rather than the best songs. The hilarious voting is the best part.
Goes on for hours. I usually get a bit bored half way through. The country that wins hosts the best years. So it’s in Switzerland this year. Last years winner was a non binary singer called Nemo.