Screw type and bayonett. Bayonett is most commonly available but screw type is easier to fit. Bayonett can ping out if you do not fit it correctly (well thats what has happened to me !)

Incandescent bulbs use a metal wire heated by electric current until it emits light. These are inefficient and produce more heat than light for the energy consumed. The lamps also have a short lifetime. But they are very cheap to make. The fluorescent lamp relies on an electric discharge in a gas. This may emit visible light (as in those pretty neon lamps) or maybe invisible ultra-violet radiation which a suitable coating on the inside of the lamp absorbs and then emits as visible light - the colour can be of a wide range depending on the material used. This lamps need complicated electronic circuit and so are about 10 times the price of the incandescent lamps. But these last 10-20 times longer and use only about a fifth as much electric energy for the same amount of light. Both lamps come in similar size and format - they can be used interchangeably in standard screw and bayonet sockets.

Vacuum and elctricity to heat the wire inside.