How do SLR cameras use light to make muscle contours clearer?

Backlight shooting means that the object you shoot is facing the sun, and the truth you shoot with your lens is facing the sun. This is the backlight.

Let the muscles outline clearly. When shooting in flash mode, the subject's body is slightly sideways, or shooting in the sun, the shadow highlights the lines more strongly.

There are more professional terms, such as spirit, exposure compensation, ISO, shutter, aperture, multiple exposure, bracketing exposure, focusing system, auto focus, manual focus, single focus, continuous focus, 3D focus and many other terms. Basically, after reading the manual, you can understand them more thoroughly.