CISC, or Complex Instruction Set Computing, is a type of computer architecture that uses a large set of instructions to perform tasks. This design allows a single instruction to execute multiple low-level operations, which can simplify programming and reduce the number of instructions needed for complex tasks. CISC architectures are commonly found in many traditional microprocessors, such as those used in personal computers. By allowing more complex instructions, CISC can improve performance for certain applications, although it may also lead to longer execution times for simpler tasks compared to other architectures like RISC (Reduced Instruction Set Computing).