Joy-Con(s) are the detachable controllers that slide onto the sides of the main Switch console. They operate wirelessly and also feature motion controls and rumble functionality for compatible games. The standard console comes with two, although none are included with Switch Lite which has its own integrated controls.
Joy-Con controllers can be used in a variety of ways depending on the game: split up, held sideways or combined to become 'one' game pad. For many games it's possible to play in two-player mode using only the two Joy-Con that come with the Switch, meaning it's the perfect system for kids who want to play games together on-the-go without the need for cumbersome extra accessories.