Lightbulb socket

Light bulbs draw their power from wires via electrical/mechanical connections.

There are many different standards for these sockets, created by de facto and by various standards bodies.

Some types of socket are listed here.

"Decorative" and standard (Edison screw) bulb bases

Mini Candelabara E-11
Candelabra E-12
European E-14
Intermediate E-17
Medium E-26 (This is what Americans call a "normal" lightbulb)
Mogul E-40

halogen bayonette styles

Bi-Post

The Bi-post base has several advantages

Bulb orientation is fixed so filament will always be in the focal plane. Filament configurations such as the C13D (coiled, zig-zagged) emit far more light perpendicular to the zig zag than parallel to it.
Sockets

Mogul Bi-post is used with searchlights, film & stage lighting fixtures 1000 watts or larger. Incandescent, halogen and HMI light sources use this design.
Medium Bi-post is used with film & stage lighting fixtures between 250 and 1000 watts (the development of the T14 base up to horizon design for ellipsoidal spotlights was one of the most important innovations of the mid 20th century)
Mini Bi-post

Bi Pin

Medium bi-pin is used on each end of a T12 florescent bulb
mini bi-pin is used with MR16 halogen bulbs

Two Pin

The 2 pin socket is an update of the bi-post design with smaller pins designed to reduce the cost of manufacture. The 1000 watt FEL medium 2 pin base halogen lamp allows designers to insert the bulb into the end of the ellipsoidal reflector through a small hole. This improves efficiency compared to the older side inserted bulb or a double ended bulb which requires two holes.

fluorescent tube standards

T-5 mini
T-8 medium
T-12 large

Specialty

Medium Medium
Three Contact Medium 3C Med
...

Phillips Compact Fluorescent types

G-23
GX23
GX32d-2
GX32d-3
...

General Electric Compact Fluorescent types

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SLI Compact Fluorescent types

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References

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