What does it mean to have a backlight when shooting?

Backlight means that light comes from the back of the subject.

Generally, most lenses use positive light or positive light, that is, the light comes from the photographer's back or left and right.

These can be classified as smooth light, and the exposure of the photographed things will be more uniform, without too much contrast and contrast, but the effect of front light will be relatively dull.

Backlight can easily lead to inaccurate metering, because the contrast is too large. If the technology of supplementary light is not used, either the subject is exposed normally and the background is overexposed, or the other way around.

But if you can make good use of backlight, you can also make good effects, such as silhouette effect at dusk.