A chipset not only refers to the controlling pieces of silicon which define the architecture and capabilities for the motherboard, but also is used to refer to an entire controlling chip for other items such as video cards.
For example, the 440BX is a motherboard chipset, the nVidia GeForce 2 GTS (the chip itself, not the video card) is a chipset, the Creative EMU10K1 is also a chipset, which is used for soundcards.
In the case of the 440BX, there are a number of chips, 2, that make up the entire chipset. Something like the i8xx series has 3 or 4, making up the whole chipset. The GeForce 2 GTS and the EMU10K1 are only single chips.