Humans are all basically very much like one another as opposed to being like other species (i.e., we have 2 arms, 2 legs, 2 eyes, 10 toes, soft skin, we like to help each other, we have the ability to think about the future and analyze things - which a worm or a clam or a tree can't, etc.) - and we all have similar human needs (i.e., we like to learn new information and develop new skills, we need love and each other).  Of course, humans need sustenance (food and water), but so do other living species for the most part. 

Although humans are very similar to each other, we each have specific genetic traits we have inherited from our parents and ancestors (like height, facial appearance, and color of hair, eyes, skin, and other genetic factors) that make us unique as individuals.  These genetic factors have been passed along from generation to generation in varying degrees.
 

These pictures show you just a few of the 2 million
known species in a very limited palette of colors.

Species come in a wonderful array of colors - 
and in incredible combinations of colors and patterns.
 

Genes, which are composed of DNA,  are inside cells of living organisms.  They store and carry an accumulation of variations of inherited biological information from parent to offspring. 

You can see some of the results of genetic diversity on the outside (as you can see in the pictures of the human being species and the photos directly above). 
Note you can see the difference in coloration on the faces of the mother horse and her offspring.  They are related so the young horse inherited genes from the mother.  The young horse also inherited genes from the father, plus ancestors on both sides.  The young horse will have its own genetic makeup (genetic diversity), and hopefully has inherited the strongest and best genes from both parents. 
The Blue-footed Boobies have inherited the genes for blue feet from their ancestors and they have inherited the genes for two feet; but the feet of one Booby won't be exactly like the feet of the other Booby. 
The two flowers are of the same species; but you can see they are different as far as the colors they inherited (same thing with the starfish).  And inside each living organism are other inherited genetic differences (i.e., possibly one starfish can move quicker and is better at survival from predators; possibly one tree will grow faster and taller, or be able to withstand drought better than the other; possibly the young horse will inherit speed capabilities and grow up to win horse races like its grandfather before him).

Living organisms contain a "history" of specific genes from their ancestry line, which makes individual living organisms of the same species different from one another in some genetic ways.  In fact, there are no exact duplicates of any (naturally created) living organism.  One thing that all living organisms share in similarity is that they can all reproduce.  If an entire species could not reproduce, it would become extinct.

Genetic diversity gives species the ability to adapt to changing environments, including new pests and diseases and new climatic conditions.