are typically types of multifaceted reflector lamps (MR), in which the number (16/11) relates to diameter of the facia in eights of an inch. For example 16 eights of an inch equals 51mm.
These lamps are typically 12 volt halogens and powered by a 240V transformer.
is a derivative of the MR16 in which typically has a similar facia but uses a bayonet type base and is 240V direct supplied.
generally found in Australia, are types of Edison screw bases. There are other sizes ranging from E5 to E40 and are common across the world. The number allocated relates to diameter of the base.
are very similar to the Edison screw bases, but are instead of a bayonet nature. These bayonet cap bases usually have 2 prongs on either side of the base and are fixed by a push and twist action.
PAR is also a unit of bulb measurement. In this system of lamp identification the first number listed denotes the maximum diameter of the lamp expressed as a number of 1/8's of an inch. For example, some common sizes are:
PAR-64's (8"), PAR-56 (7"), PAR-46 (5.75"), PAR-38 (4.75"), PAR-36 (4.5").