http://www.ngk-sparkplugs.jp/english/te ... index.html
http://www.ngk.de/en/products-technologies/spark-plugs/
http://www.ngk.de/en/technology-in-deta ... rinciples/
Also there is information about spark plug cables, glow plugs and lamda sensors.
I strongly recommend explore these sites you will learn almost all about spark plug technology


There are many diagrams and pictures that give all the information about spark plugs!
For example:

