Thermal grease is the thin layer that actually moves heat off a processor: compound applied between a CPU or GPU die and its heatsink to eliminate the microscopic air gaps that would otherwise insulate it. Without it, even a well-designed cooler cannot pull heat away efficiently, and the chip throttles or runs hotter than its design allows.
A little goes further than expected - too much compound insulates rather than conducts, so apply a thin, even layer rather than filling the gap generously. Reapplication belongs in any cooler swap, CPU upgrade, or multi-year maintenance cycle, since thermal compound dries out and loses effectiveness over time. For sustained heavy loads - workstations, servers, overclocked systems - a higher-performance compound is worth the small added cost. COLAMCO supplies thermal compound for the builds, upgrades, and maintenance business, government, and education IT programs perform.