Each participating national broadcaster chooses their artist(s) (a maximum of 6 people), and a brand new song (of a maximum of 3 minutes) through a nationally televised selection or internal selection. They need to do so each year before early October, the official deadline to send in entries.
From there, each country goes on to perform in the Contest at the end of November and is scored by a mix of public and jury vote. Of course, only one country will emerge the winner.
Watch the show from last year: