What is a 1pc toilet vs. 2pc toilet?
The poster above is right. I would add that separate one-piece toilets are usually better. According to sanitaryreview they are easier to clean, have a more powerful flush system and have standard chair seats, which makes them comfortable to use both for adults and kids.
The one piece toilet is designed so the tank and bowl are cast as a single vitreous china fixture. Typically, one-piece toilets have a lower profile than two-piece toilets. Kohler’s one-piece toilets offer some of the lowest profiles in the industry. Two piece toilets have a separate toilet tank and bowl secured to each other. They are also referred to as close-coupled toilets. Many Kohler two-piece toilets offer a 3-bolt installation system which provides a sturdy, level connection between the toilet and bowl.