DSLR stands for Digital Single Lens Reflex. Rather than viewing through a separate viewfinder, you are actually viewing through the lens so that you and the camera are seeing exactly the same thing. Typically a DSLR uses interchangeable lenses permitting the photographer to use lenses that are suited for particular purposes. See Wikipedia for an in-depth definition.
Point & Shoot is an amateur with a pocket camera (non-DSLR) in need of basic information on composing and shooting images, then transferring them to a computer for sharing.
Beginners are those who have little or no experience with their DSLR or with photo editing software and wish to learn the basics of digital photography.
Intermediate photographers have some knowledge and experience with their DSLR and photo editing software but wish to expand their skill levels.
Advanced photographers are proficient with their DSLR and photo editing software and are interested in enhancing specific skills.
A professional photographer is an individual for whom photography is the principle source of income.