A central processing unit, or CPU, is responsible for executing instructions that are given by programs. The CPU can take inputs, apply the program instructions to them and output the intended result.
A CPU can be found in many types of electronics whether it's a desktop, laptop, mobile phone or DVD player. The power of the CPU differs greatly depending on its intended use.
A CPU is known as the brains of an electronic device because it does most, if not all, of the calculations needed to function. There are other types of processors, such as an array processor, that can be used if it is undesirable to rely on a single central processor.