From the first dawn of life, all organic beings are found to resemble each other in descending degrees, so they can be classed in groups under groups.

Charles Darwin, Origin of Species, Chapter 13

Linnaean taxonomy is a hierarchical scientific classification scheme widely employed in the biological sciences. The original hierarchical structure of the scheme was developed by Carolus Linnaeus. Its current manisfestation is mardekly more complex in accordance with our vastly expanded understanding of the Tree of Life since Linnaeus's time.

Example for we humans:

When the taxonomic is uncertain, relationships uncertain, unknown or undefined, you will see: Incertae sedis, meaning "of uncertain position (seat)"