SNOT (Studs Not on the Top) is an advanced building technique which allows for more creative models, often allowing builders to add extra detailing to walls or create more interesting angles, etc.
These can be accomplished either using specialist SNOT or "with knobs" bricks and plates:
Or with items such as hinges, etc to change direction and angle.
For further reading see:
See also the Related technique of snir (Studs Not In Row)