League of Legends champions are unique characters that players control in the game. Each champion has distinct abilities, roles, and playstyles, allowing for diverse strategies during matches. Champions are categorized into different roles, such as Assassin, Tank, Support, and Mage, which define their primary functions in a team. Players can choose from over 150 champions, each with their own lore and background. Champions gain experience and gold during matches, allowing them to level up and purchase items to enhance their abilities. Understanding the strengths and weaknesses of each champion is crucial for success in League of Legends.