Yes, sodium (salt) is one of the electrolytes that we utilize during exercise -- the others are potassium, calcium, and magnesium. Oh, and there's chloride, too. When we sweat during exercise, we lose a lot of potassium and sodium. That's why you might end up with a salt lick on your helmet straps or your jersey or your shorts.
If you're craving salt, you probably aren't effectively replacing your electrolytes during exercise. For anything over 60 minutes, make sure you've got an electrolyte replacement (power, pill, drink, or gel). Follow the directions on the label to make sure you're injesting enough each hour.