Relations type=site, site=piste are used to map a 'ski ressort' or 'skiing area'.

There are relations grouping all winter sport features that are member of a particular ressort. Their name is rendered at intermediate zoom on Opensnowmap.org.

Creating relations site=piste not only allows to render nice and meaningful names on the map at low zoom, but it also come in handy when your are looking for a piste. search-sites.png

Let's say you are looking for a piste named 'sapin' (pine-tree in french). Not surprisingly, you will end up with a lot of results. However, now Opensnowmap.org gives you the results with a link to the resort name as tagged in the site=piste relation in which the piste is a member.

Handy, isn't it ? Well, there is only a few relations like this right now. But the good news is that building these relations is just armchair mapping ;)

For this, I strongly suggest the use of JOSM on bigger ressorts. Use Opensnowmap.org tiles as a background and search for "piste:type"=* or aerialway=* , the rest is your local knowledge to add the proper name.