A quad-core processor is a CPU that has four processing units in a single integrated circuit. The cores operate simultaneously in conjunction with other circuits, such as cache, memory management, and I/O ports. Quad-core processors came in 2006 as a successor to dual-core processors. More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.