Flashing is a term used for using sheet metal on structures that project vertically up from the roof to create a watertight seal between the roof and the structure.
Three Tab is a term used normally in discussing a type of roof. This is a shingle that is broke into three tabs for each individual piece
Architectural is a type of shingle that is normally heavier in weight and has more definition or depth than the shingle itself.
Square is a shingle term that is used to refer to a particular area of coverage of a shingle. One square is equal to 100 square feet.
Starter Shingle refers to the first row of shingles that are put on at the bottom of the roof. These overlap the Eave metal and are normally turned upside-down and backwards in order to produce a good straight line along the leading edge of the eave metal.
Self Sealing refers to a particular kind of shingle that has an asphalt strip underneath the shingle itself that after it is applied and with heat will seal itself to the shingle underneath it.