LEDs come in two main types, both with their own variety of package styles.

• Low power LEDs
  These include SMD and through hole LEDs to which 5mm is the most common.
  These devices only consume a fraction of a watt and require only a small current, around 20mA and powered from a low voltage source.  Due to their size, they produce perhaps 2 to 5 lumens.

  
  

• High power LEDs
  Typically classed as devices that are over 1W in power, production of >20W are in production.
  A much higher current is required typically 350mA to 1.5A and with that, additional heat is generated and needs to be thermal managed to optimise the life of the LED.
  Expect 40-80 lumens for a 1W device.

There is sometimes reference to Mid Power LEDs, such as SuperFlux or Pirhana.  Although they consume more power (~70mA) in comparison to the Low Power types, we still class them as low power.