What do you mean by "Bright" and “Dark”?

Question:

What do you mean by “Dark” and "Bright"?

Answer:

The term "Bright" refers to a photo that is lighter on the density side and may have a little higher contrast. 

The term "Dark" refers to a photo that is dark on the density side and may have a slightly lower contrast. 

Below is a sample image that shows the difference between too Dark and too Bright.