What's Triode???

I new at tube amps. Can anyone explain what's single ended triode? Thanks..
A triode is a tube with 3 grids. It is the simplest form of amplifier tube.
A triode is a vacuum tube with three ELEMENTS - a cathode, a grid, and a plate.
It might be the best method to amplify sound(music reproduction)!
There are two kinds of triodes. The directly heated triode(DHT) and the indirectly heated triode(IDHT).

With the DHT there are three elements. The plate or anode, the grid and the heater/cathode. The filament serves a dual purpose as the heater and the cathode.

With the IDHT there is the plate or anode, the grid, the cathode and the filament.

Triodes are typically low power of about ten watts or less unless run in parallel or push pull.

Don't let the low power fool you. With efficient speakers, 96db or better, they work very well.