SMB is the linux version of Windows File Sharing.
https://en.wikipedia.org/wiki/Samba_(software)
It is rather easy to use. Check out the manual, it is long but actually good. On linux, use smbclient
to mount a remote share.
It’s also quite easy to set up servers that can be accessed from both Windows and Linux, with lots of options on how to handle/simplify permissions.
CIFS is something similar that seems to be faster, but I’ve only used it as a client. On Windows, WinSCP works great with it. On linux you can use mount CIFS remote directories locally like this:
mount -t cifs //HOSTNAME/REMOTEPATH LOCALPATH -o username=USERNAME,domain=DOMAIN
.
Ask google or a good LLM for the details on this stuff :)
How did you enter this business?