Galaxies are immense collections of stars, nebulae, gas, dust, etc. They contain millions or billions of stars many of which may be planetary systems like our own Solar System. Galaxies come in all shapes and sizes from irregular to intricate and organized spirals, barred spirals, etc. Most galaxies are very far away - billions of light years, but a few are relatively near by satellites of our own Milky Way galaxy which is in turn part of a group of galaxies known as the "local group". More distant galaxies also tend to be arranged as clusters of galaxies which in turn form superclusters.