The cell is very diverse. If an object has no cell it is not alive and anything smaller than a cell is not alive because cells are the most basic units of life. There are many different types of cells and they perform many different functions.
The most common way to define cells is by classifying them into two groups, prokaryotes and eukaryotes. Prokaryotes are very simple and not quite as commonly known as eukaryotes, yet there are millions more of them in our world then eukaryotic cells. A major difference between prokaryotic cells and eukaryotic cells is that prokaryotic cells have no nucleus whereas eukaryotic cells do (eukaryote means “true nucleus”). Another difference is that eukaryotes are much larger than prokaryotes on the molecular level. Eukaryotes are most common in humans, plants, and animals where prokaryotes are mostly in bacteria (which are in humans, plants, and animals too).
As I mentioned before, cells have many functions. Eukaryotic cells are often multicellular. When a cell is multicellular it can perform even more tasks, I guess I could say that it “multitasks”! There are cells on your fingers and cells in your blood, both of those areas are very different so those cells obviously have different designs and different tasks to complete. Different cells also have different substances, proteins, and molecules in them.
There are so many ways to classify cells that it could take all day long to explain it all, but with this brief explanation you should have a better idea of how diverse cells actually are.