Classification is the process of putting something into a category. Classification of all your clothes by color may make it easier for you to put together an outfit, especially if you favor a monochrome look.
Classification involves putting things into a class or group according to particular characteristics so it’s easier to make sense of them, whether you’re organizing your shoes, your stock portfolio, or a group of invertebrates. If you’re an international spy, you might know that classification also can mean a government’s system for keeping secrets. If you have a high level of security classification, then you know really top secret stuff.