I second Chris’ answer. pi is a classic example of a transcendental number, which is a special sort of irrational number. It cannot be expressed as a fraction (irrational number) and it cannot be expressed as the answer of an algebraic equation with whole number coefficients: http://simple.wikipedia.org/wiki/Transcendental_number
pi is a never ending number, so there can be no last number.
If you ask a scientist what pi equals he/she’ll tell you it equals 3.14159.
If you ask a mathematician what pi equals and he’ll tell you pi equals the circumference of a circle divided by its diameter.
If you ask an Engineer what pi equals he’ll say “Pi? Well, it’s about 3, but we’ll call it 4 just to be safe.”
And if you ask a kid what pi is, he’ll ask if he can have ice cream with it!