This image was taken by the Advanced Camera for Surveys (ACS) on the Hubble Telescope. The Orion Nebula is a vast area of star formation approximately 1500 ly from Earth and over 3000 stars are visible in this image.
In the centre of the image is the brightest star-forming region, whose light is being generated by four massive young stars known collectively as the Trapezium. These stars can be seen in a medium-sized telescope from Earth.
To the upper left is another star-forming region called M43, but in this case the light is being produced by just one star.
Near the bottom of the image are a number of small red stars commonly known as brown dwarfs, which due to their insufficient mass have not been able to produce nuclear fusion in their cores.