The familiar pattern of X and Y chromosomes is characteristic of all mammals. Certain insects have pretty much the same kind of sex determining system, though the actual way it works is a bit different than the way mammals do it. In the X and Y system, there are two kinds of sex chromosomes, the X chromosome and the Y chromosome, which is very small. Mammals and fruit flies use this system. Grasshoppers take this pattern to an extreme.
Birds have a similar system, but it works in the opposite direction.
In many reptiles, sex determination has nothing to do with chromosomes at all. It has to do with temperature. For instance, alligator eggs which incubate at higher temperatures hatch out male baby alligators. The cooler ones hatch out females. Then there are fish.