Hierarchy of group or order to explain the Taxonomy (the study of the classification of the organisms) are:

Domain

Kingdom

Phylum or division

Class

Order

Family

Genus

Species

The domain is the highest order and species is the lowest order category.
Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1959) and Carl Woese (1977) has classified all living organisms into broad categories called kingdoms.
The five-kingdom classification was proposed by Whittaker which is Monera, Protista, Fungi, Plantae, Animalia.
The naming culture ( of the different organisms) practiced uniformly across the world is called binomial nomenclature.
Rules of nomenclature:
1. It consists of two words, the first denotes the genus (of the organism ) always begins with a capital letter and the second denotes the species , with a lower case letter.
2. It is also known as a scientific name and must be written in Italic.
3. For example- Human is Homo sapiens, the Tiger is Panthera tigris, etc.
4. It makes our work easy and convenient and provides data that can be used universally to find or look for any species whether plants or animals.
Cells are fundamentally categorized into Eukaryotes and Prokaryotes where Eukaryotes are complex in structure while prokaryotes are the smallest and simplest in structure.

In details we will be discussing in the next part.