HEREDITY

The transmission of characters (or traits) from the parents to their offspring is called heredity.
In most simple terms, heredity means continuity of features from one generation to the next.
Recognizable feature of a human being (or any other organism) like height, complexion, shape of hair, color of eyes, and shape of nose and chin, etc. are called ‘characters’ or ‘traits’.
By virtue of being the progeny of the parent, the progeny individual, need not just be the replica of what its parents are
Inheritance of characters from the parents to the progeny (i.e. ,Heredity) ensures the passing of the parental characters to the progeny

Variation- The difference or change in the characteristics between the individuals is called Variation.

Human population shows a great deal of variation.
For example, human height is a trait which shows variation.
This is because some people are very tall, some are less tall, some have medium height, some have short height whereas others are very short.
If we take a very close look at the rules of inheritance, both father and mother contribute equal amount of genetic material to the child.
This means that each trait can be influenced by both paternal and maternal genetic material – i.e, DNA.