The chipset is a collection of chips on the motherboard that form the heart of the computer by interconnecting all parts to make a working piece of equipment (the computer).
Yes, I COULD tell you about it in more detail but frankly I don't feel like there is any need for that, first of all because that would probably go the average Joe way over his head and secondly because that knowledge isn't at all necessary to operate a computer whether it is for general use or as a DAW.
If you really want to know more about how they work, there are countless hardware sites that explain it better than any of us can do in a single post.
But someone else here may be less lazy than me.
Why is one chipset is better for a DAW than another? Some perform better than others in particular fields (that even may be just in price). Some are not compatibel with certain soundcards, some are.
You know, the best part of your question is that it shows that you're actually aware of the difference a chipset can make. That puts you ahead of many others.