Up one level (Components)
An IC (Integrated circuit) is a component which contains many other components inside itself. There is a complete circuit inside the IC and it has got a special function that it should provide.
There have been made ICs with all kinds of functions. The first ICs were mainly operational amplifiers and some logic gates, but later there have been made more and more specialized ICs.
Today there are ICs which perform really complex operations, like being a complete computer by themselves. These are called microcontrollers. You can read more about them here.