What is difference between full strength butt weld and full penetration butt weld?

a weld that does exactly what it sounds like, the molten metal that is created when welding is created all the way through the materials being welded.

for example, if it is a 1/16th inch steel plate, a full penetration weld would create a molten bead from the front to the back of the plate. A full pin weld is when u have a bevel on one side that u weld first flip it over arc air gouge the other side and weld that side up