What happens when I use "RUN --type=cache,target=/root/.cache/pip,id=cache pip install flask"?

[siriusa51]

I have some questions while using buildkit, and the provided documentation doesn't seem to answer my questions adequately. Therefore, I'd like to ask here: When I include the following content in a Dockerfile:

dockerfile

# ...
RUN --type=cache,target=/root/.cache/pip,id=cache pip install flask
# ...

What operations will buildkit actually perform, and is it possible to mount the directory specified by the buildkitd server into /root/.cache/pip in the Dockerfile?