LED lamps come in different shapes and sizes but also in different base types. It is important to get the LED bulb with the correct base to match the lamp socket it will be installed in.
Light Bulb Base Types
Edison bases are the most common base types for LED bulbs. Also called screw-in bases, these vary in size but all are typically "screwed in" to the socket, clockwise to put in and counter-clockwise to take out. Edison bases are commonly used in A lamps, BR lamps and PAR lamps, as well as decorative lamps like candelabras and globes.
Bi-pin bases are found in smaller bulbs like MR16 lamps, and have two pins as the point of contact with the socket. One of the most common types is the GU5.3 base. These bases are simply plugged in or pulled out from the socket.
For tube lamps, the base types include the traditional G13 medium bi-pin for T8 lamps, G5 mini bi-pin for T5 lamps, and Fa8 or R17d for 8ft T8 lamps. Other lamp base types include bayonet base for miniature bulbs, wedge bases and festoon bases. In the case of CFL and PL lamps, these bulbs have special bases that have 2-pin or 4-pin configurations that fit into square sockets.
See how the different lamp base types compare to each other by clicking on the image below: