This portion is what you see when you're looking straight at the engine from the front. The fan blades you see we'll get into later, however you can imagine air being forced into the engine from this stage.
2)Compression
At this point the air that made it into the engine goes through a serious of smaller fan blades, similar to what you see when looking at the engine. These smaller blades compress (compact) the air.
3)Ignition
At this point, when the air has been compressed it is moved into a chamber where jet fuel is squirted into the mixer using spray nossels. Also at this stage is an igniter which creates the spark to light the fuel air mixture.
4)Exhaust
At this point the air is heated and forced towards the rear of the engine. At this point it goes through another series of fan blades while it decompresses. After the remaining exhaust fan blades it exits the engine through the rear.
Now... why so man fan blades inside the engine?
Lets start with the small ones that compress the air. These help make a ratio of compressed air to fuel for proper burning.
The exhaust fan blades are used to turn the large fan blade you see when looking at the engine from the front. So when the air turns the exhaust blades, that is linked up through a straight shaft that turns the giant fan blade. This moves air through the engine AND also through the engine cowling. Depending on the engine 80 percent of the forced air goes through the engine and the other 20 percent flows over the engine and propells the aircraft forward.