What does al dente mean literally?
"Al dente" is a notion used in cookery which describes the state of readiness of pasta mostly (but the technique is also applicable to grains, beans or vegetables). The products are cooked in a way to preserve their natural "bounce" so it may even seem that they are undercooked. However, pasta cooked "al dente" if cooked properly shouldn't be sticky or of irregular color.
In order to check whether the current consistency of the pasta is close enough to the ideal one, chefs usually bite a small piece to taste it. That's why the Italian term "al dente" is translated to English as "to the tooth".