Betelgeuse is a red supergiant in the constellation of Orion. It's bright red colour and position as Orion's right shoulder make it unmistakable.
If you could place Betelgeuse where our Sun is it would engulf all of the planets up to and probably including Mars.
Image: At this small scale Betelgeuse dwarfs our Sun which appears as a small dot a few pixels wide.
Betelgeuse is one of three stars which form the asterism, the Winter Triangle.