Resistors have several properties besides their rated resistance, such as their temperature coefficient, resistor noise and power rating. These resistor properties can be important to take into account depending on the application.
Resistor types: You can find several different types of resistor. The most used resistors are fixed value resistors, but also variable resistors are very common. The most used variable resistors are the potentiometer and rheostat. On the other hand there are a lot of resistors which have a variable resistance which is dependent on external factors such as temperature, light, voltage or magnetic fields.
Resistor materials: Resistors can be produced in several ways based on different materials. These different materials all have their own characteristics. One of the most used resistors nowadays is the carbon film resistor, other material resistors include: carbon composition resistors, metal film resistors, metal oxide film resistors, foil resistors and wire-wound resistors.
Resistor applications: Resistors are used in numerous applications, including almost every circuit and electric device. A frequent application in hobby projects is to use a resistor for a LED, to limit the current that will flow through the LED.