What do we mean by 'the process of evolution'?

Evolution is the constant state of change of any living
organism regardless of whether it is a tree, an animal, or a human being.  As beings
react to their environments certain traits get passed along through genes that enhance
the possibility of survival.  There are several trains of thought on why this happens,
and the most popular this day and age is that of natural selection.  Essentially what
happens is that the physical attributes, and beahviour patterns in any given living
organism that are most beneficial to survival continue on through the genes because
those living organisms possessing those traits are more likely to survive and pass them
on to their offspring.  The better a species is at adapating to changes, especially
environmental changes, the longer that species is likely to survive over
time.

Another process of evolution is that of extinction. 
By that I don't mean of a species, but of physical attributes and behaviour patterns in
a species that become obosolete as a species evolves.  For instance, in x-rays of whale
flippers one can see the remains of what look quite like human hands.  As the whale
ancestor spent more and more time in the water, these "hands" became less necessary and
so overtime they were absorbed into the body.