Indentify the part of the lamp that connects into the light fitting this is generally known either as the “cap” or “base”. This provides the electrical contact and also often the physical location of the lamp. A vast variety of caps and bases exist in order to help make sure that only the correct type of lamp is used in any given fitting. This section shows many of the most popular fittings.

 
A general guide to help you identify a lightbulb - Click Here

2 Pin (Tubes) Halogen Base - G Series Goliath Base (E40) Other Base Types