A processor core (or simply “core”) is an individual processor within a CPU. Many computers today have multi-core processors, meaning the CPU contains more than one core.
For many years, computer CPUs only had a single core. In the early 2000s, as processor clock speeds began plateauing, CPU manufacturers needed to find other ways to increase processing performance. Initially, they achieved this by putting multiple processors in high-end computers. While this was effective, it added significant cost to the computers and the multiprocessing performance was limited by the bus speed between the CPUs.
By combining processors on a single chip, CPU manufactures were able to increase performance more efficiently at a lower cost. The individual processing units became known as “cores” rather than processors. In the mid-2000s, dual-core and quad-core CPUs began replacing multi-processor configurations. While initially only high-end computers contained multiple cores, today nearly all PCs have multi-core processors.
NOTE: “Core” is also the name of Intel’s processor line, which replaced the Pentium lineup in 2006. Examples of Intel Core processors include the Core Duo, Core 2, Core i3, Core i5, and Core i7.