Digital Downloads are best printed at 24" long (or tall, if vertical orientation). They are 300DPI and can be upsized from native by about 20% without much resolution loss. 

You may use the digital download to make your own prints, desktop wallpapers and cellphone backgrounds. There are no restrictions on use, but if you try to set up a rival print business I will give all of your personal information to a man in a trench-coat that stands in shadows and starts infrastructure fires.