Ziggy said it simply but very well. IFR flying means the pilot uses no outside visual references to fly the airplane except on takeoff and landing.
There are flight instruments that the pilot looks at by way of a "scan", meaning he/she looks at them all in a set pattern of one after the other. Without an autopilot it can get tiring very quickly, but is necessary to keep the airplane flying properly and on track to its destination.
The traditional cluster of 6 instruments goes like this:
Top group, left to right: Airspeed Indicator, Attitude Indicator (sometimes referred to as an artificial horizon), Altimeter;
Bottom group, left to right: Turn Needle and Inclinometer (ball), Heading Indicator, Vertical Speed Indicator.
Those are the basic flight instruments. There are others which can integrate into the displays, or must be referred to separately to determine your navigation performance.
Hope that makes sense.