More information on the Filesystem Hierarchy Standard is available from Wikipedia at https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard or from the Linux Foundation at https://wiki.linuxfoundation.org/lsb/fhs
From https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch03s17.html :
This main purpose of specifying this is so that users may find the
location of the data files for a particular service, and so that
services which require a single tree for readonly data, writable data
and scripts (such as cgi scripts) can be reasonably placed. Data that
is only of interest to a specific user should go in that users' home
directory. If the directory and file structure of the data is not
exposed to consumers, it should go in /var/lib.
The methodology used to name subdirectories of /srv is unspecified as
there is currently no consensus on how this should be done. One method
for structuring data under /srv is by protocol, eg. ftp, rsync, www,
and cvs. On large systems it can be useful to structure /srv by
administrative context, such as /srv/physics/www, /srv/compsci/cvs,
etc. This setup will differ from host to host.
Therefore, no program
should rely on a specific subdirectory structure of /srv existing or
data necessarily being stored in /srv. However /srv should always
exist on FHS compliant systems and should be used as the default
location for such data.
Distributions must take care not to remove locally placed files in these directories without administrator permission.
This is where you put the (static?) data for your servers, http, ftp, etc ....
