There is a difference, as follows:

1. Chairs have backrests

Chairs usually have four legs, a seat and a backrest. They can include arms or footrests. Most models have wood, metal or plastic frames with a variety of padding and fabric options. Chairs come with backrests and some have arms, stools come without backrests or arms.

2. Stools are more space-efficient

Working in a limited room, stools typically have a smaller footprint and bottomless models are easy to store under a table or counter. Chairs, by contrast, take up more space, which can be problematic for saving square footage or seating all your guests.

3. Comfort Differences

With chairs, ergonomics is a key factor. Because backless stools lack lumbar support, they are best suited for areas of occasional or short-term use, such as bars and breakfast nooks.

High-backed chairs and plush seating offer more structure, inviting guests to settle in and dine comfortably for longer periods of time. Chairs have the function of a bed of sorts, allowing you to rest on the backrest; stools do not have the function of reclining.

Baidu Encyclopedia - Chair

Baidu Encyclopedia - Stool