Tube Terminology Question..

ive been into tubes for over 15 years yet tube terminology still escapes me...Can someone here kindly Define the various parts of a tube and what they are called and how they define the sound...terms like Getter, Black Plates, Side plates, why sometimes tubes like a 6sn7 has a silver or chrome substence which drips down from the top of the tube.....D getters?, please be as comprehensive as possible...

TIA