One should keep in mind the distinction between ‘Joint’ and ‘Weld’ types, the former describes the configuration of the steel parts relative to each other, while the latter refers to the type of weld employed to hold the parts together.
There are 5 basic joint types, they include: Butt, Tee, Corner, Lap, and Edge. Note that in all cases, except the ‘Butt’ either groove or fillet welds may be used.
Almost all the welds used to make the joints fall into 2 basic types, Fillet welds and Groove or Butt welds. A groove weld can be defined as one in which the weld metal lies within the outline, in cross-section, of the parts connected, whereas a Fillet weld is one where the weld metal forms a fillet between the faces of the adjoining parts. Groove welds can be further sub-divided into, Square, Bevel, Vee, U, and J depending on the form of plate edge preparation adopted to accommodate the weld. Fillet welds are usually located between adjacent faces at 90 degrees to each other, although the angle may vary between 60 and 120 degrees.