Bomber command was part of the Royal Air Force. It was probably the main and most influential division of the Royal Air Force, having many great deeds accredited to its name. Its aims were simple, destroy as much as possible, and this it did, with numerous impressive battles won by the allies, which very much couldn't have been won without the Bomber Command.
As noted above, the aims of the bomber command were very simple. They had to destroy as much as they could. Focusing on factories that produced weapons, tanks, planes etc, was the logical part of it, and only one part of it. The other part was taken from the Germans. The German's bombed London repeatedly, on a a twenty four hour basis, and for a very long time too. This was psychological warfare, and it worked. It lowered morale, and it obviously killed off a lot of the population.
When the RAF first tried this however, it didn't work particularly well. Primitive technology and equipment made it very tough to come out of each flight alive. A good example of this is from Source B, when under heavy strain, and enemy fire, the equipment starts to fail. The specific equipment mentioned in this source is the altimeter, showing zero feet while in the air.
Bomber Command, though amazingly effective towards the end of the war, could not be given that same sort of honour at the beginning of its operations. During the early months of the war, Bomber Command's attacks were a mere nuisance to the enemy. This of course led to horrible losses, and so, because of this, the planes had to fly in the dark. Plane navigation in those days however, wasn't the easy task of pressing a button that it is today.