Standard height toilets have seats that stand 13 to 16 inches from the ground. They are becoming scarce as manufacturers try to accommodate as broad an audience as possible with their seat heights. The benefit of standard toilets is they are great for children and shorter people, but not so great for those with mobility issues and taller people.
Comfort height toilets follow the ADA (Americans with Disabilities Act) guidelines, which state that the seat should be between 17 and 19 inches high to make it easier for the less able to sit and stand.
Some manufacturers have gone one step further and produced universal height toilets with seats as tall as 21 inches.