Essentially, this allows you to mount a folder on a remote system accessed via SFTP as a drive on your system.
There are occasional hiccups when internet connection is spotty, but my experience has been largely positive. Transfers to and fro are quick and easy.
You mentioned running Linux on your Chromebook in your question so chances are you're already familiar with this. This allows you to install a complete Linux distro of your choice as a
chroot and run it simultaneously (not dual boot) with your normal Chrome OS system.
You then have access to a much wider range of FTP clients, including Filezilla, gFTP and LFTP. If you use the
xiwi target, you can actually run these as a normal window in your Chrome OS system without having to switch between the two.