This is listed on the gvldash page.
It enables the open sharing of files e.g. PNG plot outputs from pipeline analyses.
To get files to appear here you must write them to the directory:
/mnt/galaxy/home/researcher/public_html
NB root (i.e.sudo) permission is needed to do this.(so ubuntu account is OK).
You can also stick .html files in there and view them interactively, like the output from Krona for visualising community composition, or the output of MultiQC for summarising the quality of various stages of a sequence analysis pipeline (trimming, FastQC, mapping, annotation).