Stain differs from paint in several different ways. Some stains are meant to do little more than accent the natural grain of the wood. They are common with hardwoods like oak, ash, and maple. Stain usually isn’t applied to softwoods like pine, as they tend to mute certain aspects of the wood grain.
There are other types of stain that have significant coloration to them. Some of them are meant to mimic the appearance of a different type of wood. One of the more common examples that were popular in the 1980s, was to take oak and then apply a dark walnut stain to it. This would allow relatively affordable oak, look like premium price walnut wood. There are many combinations like this including red oak, golden oak, cherry, walnut, and fruitwood, just to name a few.