The story levels are a touch-typing course arranged as a game. You begin on the home row — A, S, D, F under the left hand and J, K, L and the semicolon under the right — and each level adds a small number of new keys to the ones you already know. Nothing asks for a key you have not been shown.
Levels are short on purpose. Finishing one takes a minute or two and awards up to three stars based on your speed and accuracy, so there is a reason to go back and beat an earlier attempt rather than grinding forward through material you have not absorbed. Zones unlock as you accumulate experience, and each zone widens the keyboard: top row, bottom row, numbers, then symbols and fluency.
This is the right place to start if you are learning to touch type properly rather than looking to test a speed you already have.
Also try: the touch typing guide · free practice