Variation can either caused by inheritance, the genes that you inherit from
your mother or father. But it can also be caused by environmental factors
An example of this is, eye color. Eye color can differ due to the genes you
receive from your mother or father. However the eye color cannot differ due
to environmental factors.
Environmental factors can also influence your characteristics. A prime
example of this is weight, which can be determined by how much one eats.
Height can also be determined by environmental factors but it can also be
determined by inherited factors.
Variation is either continuous or discontinuous. Continuous variation has
data in which the values vary across a range.
An example of this is height, where there is a continuous variation. The
range could vary from 130cm to 200cm. This data is usually highlighted in
a line graph.