How can portrait photography achieve a true foreground and an empty background? Thank you, everyone.

This phenomenon is called depth of field. There are two factors that affect the depth of field. One is that the longer the focal length of the lens, the greater the depth of field. The other is that the smaller the aperture, the greater the depth of field ... it's easy to understand ~ just do an experiment. You put an object beside you. You zoom in to the maximum (see your lens is 25-85- 85) and focus on the subject. The aperture can be adjusted. Just try more!