Lego (trademarked in capitals as LEGO) is a line of construction toys manufactured by the Lego Group, a privately held company based in Billund, Denmark. The company's flagship product, Lego, consists of colorful interlocking plastic bricks and an accompanying array of gears, minifigures and various other parts. Lego bricks can be assembled and connected in many ways, to construct such objects as vehicles, buildings, and even working robots. Anything constructed can then be taken apart again, and the pieces used to make other objects. The toys were originally designed in the 1940s in Europe and have achieved an international appeal, with an extensive subculture that supports Lego movies, games, video games, competitions, and four Lego themed amusement parks.
So, in other words, Legos are fun toys where you put together blocks and build stuff. It is also a very popular toy and a very expensive one, but hey, it's worth it.