Think of it this way. All your computer components are cars, trying to get this way and that. The motherboard is the road, where the cars are driving, and the CPU is a traffic light, telling the cars when they can do what they want. The chipset is basically the person that sits on the street corner and changes the lights (if such a person existed in real life).
Basically, the chipset has a big part to play in your system's stability, as well as deciding what features your motherboard has.
Examples of chipsets with <font color=blue>manufacturer</font color=blue> and <font color=red>model</font color=red>: <font color=blue>Via</font color=blue> <font color=red>KT266a</font color=red>, <font color=blue>SiS</font color=blue> <font color=red>735</font color=red>, <font color=blue>Ali</font color=blue> <font color=red>Magik 1</font color=red>, <font color=blue>Intel</font color=blue> <font color=red>i850</font color=red>. Hope that helps.
<font color=orange>Quarter</font color=orange> <font color=blue>Pounder</font color=blue> <font color=orange>Inside</font color=orange>