What are the black point and white point of an image, and why are they important?

What will be an ideal response?

Every image has a black point, representing the darkest pixel in the image, and a white point, representing the brightest pixel in the image. In other words, the black and white points represent the start and the end of the tonal range of the image.

Black and white points have a substantial effect on contrast. Often, photographers will capture an image with settings defined that the darkest pixel be no darker than, say, 15, and the brightest no lighter than 240. This forces the camera not to make shadows too dark or highlights too white. It results in an image that has a smooth tonal range from shadow to highlight but still lacks contrast because the darkest shadows aren't dark enough and the whitest highlights aren't white enough. This can be fixed using a Levels adjustment.