Processor is the heart of the computer. Whatever you see in the computer are executed as computer instructions in the processor. Whatever you are doing in the computer goes through processor be it surfing the internet, writing an essay in Word, or chatting with friend on social network.
This is the reason that major measurement criteria for processor is its speed which is represented in GHz (Giga Hertz). More the GHz's more the speed of the processor.
Intel has been major vendor of processors since long however recently another player AMD has joined the race for processors. However still the market is dominated by Intel processors.