The halogen dichroic lamp consists of a normal halogen bulb mounted in a dichroic reflector and often sealed behind a glass 'lid'. These lamps is usualy operated at 12V DC, and used for spotlights, downlights and desklamps.

The dichroic reflector acts as a mirror for visible light but will let most of the infrared(heat) through. This means that the light from these lamps are colder than light from other halogen lamps.
 
        Power 
      connectors
         |  |
        .|__|.
        |    |
       .|____|.
      /  ||||  \ dichroic reflector
     /   |--|   \
    |     \/     |
    |    bulb    |
     """"""""""""
     protective
       glass

The protective glass is there to prevent someone from touching the bulb.
An important thing to remember when fitting these lamps, especially in downlight applications, is that the heat from the lamp may ignite flameable things like newspapers and wood. Therefore the area over the lamp most be free of flameables.