Describe the organism (physical appearance, habitat, function, history,

To put it simply these cells are technically termed as Eukaryotic (multi-celled) and Prokaryotic (single-celled) cells.
There are differences between Eukaryotic and Prokaryotic cells. This difference is considered to be the most important distinction between groups of organisms. A Prokaryotic cell does not contain a nucleus. It only contains one chromosome and is a single-celled organism. It was the only form of life on earth for millions of years. Examples of a Prokaryotic cell are the different types of bacteria present today. 
A Eukaryotic cell contains a nucleus; more than one chromosome and is typically a multi-celled organism.  Both plant and animal cells are eukaryotic cells.

The advantage is that eukaryotic cells have a nucleus which functions formally as to store the DNA of the cell which can translate into many functions such as cell division and work structure between cells that forms the hierarchial function to tissues.

Where are they though?

Ha ha it happens bro