A biological classification nomenclature intended to organize the vast number of known plants and animals into categories that could be named, remembered, and discussed. Modern classifications attempt to show the evolutionary relationships among organisms.
We all owe a great debt of gratitude to Carolus Linnaeus, the father of taxonomy, who whittled away most of his opportunities with women in order to provide us with this hierarchy.
I've also added the 'Domain' level above Linnaeus top level of Kingdom. I don't have many opportunities with women either.
You can use the Taxonomy Mnemonic to help you remember this list if you're simple or have hit your head a lot.