A chipset is the set of support chips on a motherboard that manages the flow of data between the CPU, memory, and peripherals.1
Overview
Historically a PC chipset split into a northbridge (fast links to memory and graphics) and a southbridge (slower I/O like storage, USB, and audio). As CPUs absorbed the memory controller and graphics link onto the die, the northbridge’s job moved into the processor, leaving a single I/O hub — Intel calls it the Platform Controller Hub (PCH). Today the chipset mainly provides the extra PCIe lanes, USB ports, SATA connectors, and other I/O that a platform exposes.
Where it fits
The chipset, paired with a given CPU socket, defines much of what a board can do: how many devices it supports, which features are enabled, and how peripherals reach the processor over the system bus. It works alongside the board’s BIOS/UEFI firmware at startup. On a single-board computer the chipset’s functions are folded into the system-on-a-chip, so a GopherTrunk capture node has no separate chipset — but the connectivity it provides is the same idea.