A lamp holder is the device for holding a light bulb or lamp, most light fittings or luminaires have a lamp holder. It's a fundamental element of most fixtures which also provides the circuit connection to ensure reliable power. Also referred to as a light bulb holder, it's available in various types according to the application requirements.  

As per the materials used, there are porcelain lamp holder /ceramic light socket, plastic lamp holder (bakelite lamp holder/ thermal plastic lamp holder, etc), metal lamp holder. As per the applications, there are

>>Edison Screw Lamp Holders : E27, E14, E40, E10, E12, etc

E27 porcelain lamp holder, IP20, IP54, glazed, in white, black,brown, marble and other colors for option, usually use for home decoration, diy lighting and vintage lighting fixtures, etc	E40 ceramic lamp socket, without glazed, suitable for street lighting, warehouse lighting, etc

>>Halogen Lamp Holders , such as GU10, G9, R7s, MR16, G8, PGZ10, etc

GU10 GZ10 lamp holders	MR16 G5.3 lamp holders	G9 lamp holders

>>Compact Fluorescent Lamp Holders: G24q, T8, T12

>>Batten Lamp Holders

black porcelain batten lamp holder E27, IP20	black angled porcelain batten lamp holder E27, IP20

>>Vintage Lamp Holders

The vintage lamp holders are widely used in indoor lightings, the vintage lamp holders include colorful porcelain lampholder and metal lamp holders; and the metal lamp holders are usually made from brass, iron and aluminum, three materials.

Black Porcelain Lamp Holder, full glazed, suitable for pendant lighting, wall lights,etc	Metal lamp holder with shade ring , made from iron with a porcelain core inside	Metal lamp holder with switch, made from brass, nickel plating	Vintage Lampholders made from aluminum in chrome, copper, gold and other finish for option, with a plastic socket inside.

>>Metal Halide Lamp Holders:

>>Medium-Base Lamp Holders: E26

>>Mogul-Base Lamp Holders: E39

>>Bayonet-Base Lamp Holders: B22, B15

As per the IP class, there are IP20(for indoor use only）, IP44 and IP54, etc. The IP54 & IP44 are waterproof lamp holders, suitable for bathroom and outdoor use.

IP54 waterproof porcelain wall lamp holder and wall lights E27	E27 angled waterproof porcelain lamp holder and sauna lamp IP54	E27 IP20 porcelain lamp holder and wall light

Regarding to the porcelain edison screw lamp sockets, there are glazed or without glazed for options. The top quality porcelain lighting fitting, are always full glazed in black,white,brown,red,yellow and other colours for option, that's beautiful and elegant for home decoration, diy lighting,home and bathroom innovation; such items are always as an indivisible part of complete lighting fixure and appear outside.

About the porcelain lamp holder without glazed, usually use as a lamp socket only and put inside of lighting fixtures.

E27, IP20, porcelain lamp holder in different colours for option, suitable for suspened pendant light, wall lights, etc	E27, IP20, porcelain hanging lamp holder, for pendant lighting	E27, IP20, non-glazed