What are the two types of variation?

Genetic and environmental.

Genetic is "hard coded"into the DNA and RNA of the plant or animal, where as environmental is the physical expression of the genetic - this may vary according to environmental conditions and pressures.

A simple example is that a Ficus tree will have large, dark green leaves when in its natural semi-tropical environment, however if the same plant was to be transported to a hot, dry area the leaves would eventually decrease in size and colour in order to reduce the amount of water lost by the plant (and possibly sun burn)