Get your own printed copy of the Factory Triumph Parts List for your model Thumbing through the detailed exploded drawings and specifications will teach you plenty ... even if you don't need any parts right now.
From the wee singles through the twins and triples, from 1939 to 1985, they're all here:
Triumph Parts Listings in this section cover Triumph models starting in 1939 where the engine and gearbox are housed in separate castings (this became known as pre-Unit Construction after the advent of later models where the engine and gearbox were housed in a single casting)
There is nothing like holding the factory replacement parts listing in your hands when sorting out the parts you need.
Our professionally made, coil bound copies open fully flat on the bench so you don't lose your place when delving in deeper...