In brief
background-clip limits the background painting area, for example to content-box or padding-box. This differs from positioning the image itself.
Useful to know
background-clip limits the background painting area, for example to content-box or padding-box. This differs from positioning the image itself. [1]
The distinction is especially visible with transparent borders. If colour appears beneath a border, inspect the painting area. Moving the image with background-position addresses a different problem.
Sources
For further detail and to check the information: