A snow scene or a night shot or concert shot will fool a light meter. To cure this some photographers use a spot meter which mesures only a small portion of a scene or frame. Hard light throws distinct shadows. It comes from a point light source such as the sun or an electronic flash. It is a harsh light and often can cause the subject if it is a person to squint or need to put on sun glasses.
Soft light is the opposite and comes from a reflected source or a broad source.
It is often indirect light and is frequently found in the shade as light that reflects into the shade from the surroundings. Light quality is effected mostly by change in subject or camera position or the use of reflectors or fill flash. A soft light is used for more subtle effects . Hard light can further be broken down according to its direction where it might come from the front, side, back or top of the subject. The direction of light will determine where shadows will be.