Q) What does "al dente" mean when cooking pasta?

Al dente is a fancy term for pasta that's fully cooked, but not overly soft. The phrase is Italian for "to the tooth," which comes from testing the pasta's consistency with your teeth.
How does one cook pasta "just right"? According to the National Pasta Association:

Boil 4 to 6 quarts of water for one pound of dry pasta.
Stir in the pasta and return the water to a boil.
Stir the pasta occasionally during cooking.
Follow the package directions for cooking times.
Nibble the pasta to see if it's done. Here we return to our old friend "al dente" -- firm to the bite, yet cooked through.
Drain pasta immediately (otherwise it'll keep cooking itself). You're done. You're just right. You're al dente.