Your undertones and your skin tone are two different things, but your undertones will predicate the warmth of your foundation. The three undertone categories are cool, neutral, and warm. People with cool undertones look good in silver jewelry, and their skin has a pink, red, or blue hue.
Neutral undertones can be a bit trickier because your skin is neither warm nor cool. A quick way to see if you possibly have neutral undertones is to see if both gold and silver jewelry look good on you.
And finally, people with warm undertones look good in gold, and their skin has a yellow, gold, or peach tone to it.