Nintendo Labo is a system of cardboard objects that you construct and which interact with the Switch in novel ways using the various features of the system's Joy-Con controllers. For example, you can construct a wearable Robot kit which registers your movements in-game, or use the system to experience some simple Virtual Reality games. It's ingenious, although beware that with younger children you will be called upon to do the lion's share of the building, which can take several hours.
Due to the required features and design of the Nintendo Labo kits, they are only compatible with the standard Switch model and will not work correctly with Switch Lite. Switch OLED is also slightly bigger than the standard model, so compatibility is not guaranteed.