Quantity:

What does the quantity of light entering the camera affect:

The quantity of light entering the camera affects the object you're shooting. When you have lower quantity of light you automatically have a lower shutter speed, too. So it's neccessary that you go closer to the object with your camera that it can get the right shutterspeed that is needed.
It also affects the depth of field, the higher the quantity of light, the the lower is the depth of field.
The contrast also can be higher when you have a higher quantity of light.


Quality:

What is soft (difused) light?What type of source does it come from?What effect does it have?
soft or defused light is light that is not real harsh and soread out.
It eighter comes from a lighter space or artificial defuser. It also can come from an indirect light, that is bounced off from sometging else. all in all it makes the the object lighter.

What is hard (direct) light?What type of source does it come from?What effect does it have?
hard light is a light that goes directly from the source to the object. For example the sun or a direct flash are hard lights.
The effect is that the object is really bright and you have to be careful that it isn't too bright for seeing the details. When you stand directly infront of a person and the backround is darker and you use a hard flash you probably won't see any details in the object.


Direction:
What is front light good for?What is front light bad for?
It's good for seeing the details and it's a neutral wy of shooting sth, so you don't see that there is light shining on the object.
But it;s bad for seeing details in the backround and you often can't find any visual clues that it's an 3-dimensional object, because there are no shadows.

What is side light good for?What is side light bad for?
Side light is good for adding depth and you get a really good 3-D effect. Sometimes it also brings a mysterious effect with it.
It's bad for seeing deatils , because normally one half is in shadow.

What is back light good for?What is a possible problem with back light
Backlight is really good for creating a silhouette (when more light is coming from the backround than bouncing off the object). it's also good for seeing the backround.
One possible problem that you can't see the details of the object.