kruz,
Triplock refers to the gasket system used in the tube- There's a gasket at the base of the tube where it threads to the case, another inside the tube to seal at the stem, and of course, the gasket on the outside of the threads that mate to the crown.
Twinlock is the same concept, except a smaller diameter crown/tube (6mm vs. 7mm) and minus the gasket outside of the tube.
Technically, there is also a gasket inside the crown to compress against the inside edges of the tube, but that one isn't counted into the figure