Category of Resistors
There are various types of resistors if you combine function, shape, resistive material and its purposes.
Categorized by function, there are three types of resistors; fixed resistors, used in a electric circuit; trimmer potentiometer to adjust a circuit; variable resistor, used as a radio volume by changing the resistance.
Fixed resistors are divided into lead type(with lead wire) and surface mount type without lead wire. Surface mount type includes rectangular type and cylinder type. Resistors are more divided into resin mold type and ceramic type, etc depending on cealing material.
The materials of resistive body includes more; Film type that includes carbon film, metal film that applies Nicrom, metal oxide film and metal glaze composited by metal oxide and glass; metal plate, metal wire, those that apply metal foil; solid type that applies metal oxide ceramics.
The purposes of resistor are different depending on resistance tolerance, temperature characteristics, high voltage type, surge resistant type, fusing type and temperature characteristic that changes resistance. You have to select a suitable resistor for your purpose depending on combinations mentioned above.