Ensuite or En Suite is a bathroom that is adjacent, and only accessed from, a bedroom. This is most commonly seen as the master bathroom accessed from the master bedroom. Pronounced "ON-sweet".
A Jack & Jill bathroom is a bathroom located between two bedrooms with access from each bedroom. With 2 doors, it usually has no door or access to a hallway or common area.
Bathrooms with only a sink and toilet are Powder rooms, although they can also be called a half-bath. Powder rooms are often located near common areas instead of near bedrooms so they are easily available to guests. In a two-story house the powder room is almost always found on the first floor.