A bi-level has two floors. The door usually opens in the center of the front facade onto two half flights of stairs, one going up to the main living level, one down. The lower floor is half underground but has standard size windows, and there are often bedrooms, sometimes a laundry and/or bath on that floor. The upper stairs usually open into an open, or a semi-open living/dining/kitchen to one side and a short hall to the other leading to (normally two) bedrooms and a bathroom.
A split level home has three floors. Just like the bi-level, it has two half flights of stairs, one up, leading to bedrooms and baths, one down to either extra bedrooms or a family room. Unlike the bi-level, the front door usually opens into an open concept living/dining/kitchen area, often with a door to the garage, if a garage is attached. This side of the house is a single story and frequently offers cathedral ceilings. The stairs usually run perpendicular to the front door, and lead into a two Storey section, with, again, one half of the lower story underground. Actually, split-levels can be more complex, offering additional levels – a basement, for example, under the main living floor. I’ve even been in a five-level split. this type of house also offers more design flexibility, so that, although there is a pretty standard plan accounting for most of& them, some can come with more unusual layouts
Bi-Level, the difference is, with a split-level, the stairs run, in half flights, from one living level to another, with a bi-level the stairs run, by half flights, up and down from a very small foyer, not from a living level.