Hard light vs soft light.

Lighting is one of the most important aspects of photography that a photographer has to consider.
The lighting in a composition is effected by many different factors, and lighting drastically affects your images. 

This can be how hard/soft your lighting is, or the direction of your lighting.
Soft light and hard light are two very different things. Soft light creates faded, less harsh shadows while reducing contrast and overexposure. Hard light creates distinct shadows with a higher contrast, saturation and often overexposed

This image is an example of hard light. The charger is overexposed, and the shadows in the background are 'hard' (well defined).

This image is an example of soft light. The charger is not over exposed. You can see more detail than in the first, overexposed, image. The overall contrast of the image is lower meaning the colours are less bright, and the shadows are softer.