Set where black and white sit in a clip. Levels maps a chosen input range onto the full output range, the most direct fix for washed-out, foggy, or low-contrast footage.
Black point, white point, gamma
Raise Black Point until the darkest areas are truly black. Lower White Point until the brightest areas are white. Then use the midtone Gamma to set the overall brightness. Values pushed past the points clip, so watch highlights on faces and sky.
Consistent levels
The values are fixed for the whole clip. Pause on the frame with the darkest shadows and brightest highlights you care about, set the points there, and check a few other frames before exporting.