Waldhütten are buildings near or in a forest, normally found near a village. They are often accessibly through a forest track or sometimes even a paved road. Cars are meant to access the building in order to bring supplies or even guests. The WALDHÜTTE itself can be rented by locals (non-locals can't access it or have to pay a higher fee). Its operators may vary: city council or related (e.g. forestry, game warden, municipal works service), associations (e.g. gun club, women's club, gymnastic club etc, scouts.) or individuals. In the majority of cases they are associated with the community and public life and thus known by almost all inhabitants of a village/region. The capacity is around 20-60 people. There may exist smaller or bigger ones.
They are equipped with furniture (tables, chairs, benches), a kitchen including kitchen utensils and dishes etc. and a toliet. Mostly they lack beds since there is often only one big room. Depending on the area you're in you'll normally find electricity and hot / cold running water. The outside is often equipped with a pic-nic site including a fire place and some water source. They can be used by public at any time.
The main goal of those WALDHÜTTEN is simple: offer a place to invite a lot of guests and party in a natural environment where you don't disturb anyone, fully equipped so you only have to bring food and drinks. They shall be used by clubs but also by individuals. If the WALDHÜTTE is unrented, it remains closed and you only have access to the pic-nic site.
In Switzerland and Germany those WALDHÜTTEN are very common; almost every village in a rural environment has one. Even in the agglomeration of big cities you will find WALDHÜTTEN. They can be distinguished from other community centers by thir specific appearance and usage. They are used frequently by old but also by young people for meetings, parties or other activities.
Even if unrented and thus closed the roof overhang can offer some form of shelter and the pic-nic site is a good recreation spot. Since they are easily accessible and known by almost anyone WALDHÜTTEN can serve as point of reference and landmark (their location can be found on guideposts and signs.). And as WALDHÜTTEN are used for parties and thus need to be found by non-locals and often lack a specific postal address or street name (forest!), they need a representation on a map that differs from a simple building.
The tag tourism=alpine_hut is not suitable but currently sometimes used. It is clearly no alpine hut: most time it remains closed and offers no real form of shelter or place to sleep. You won't find any food or beverage. And it is not located in the mountains.
again, the tag amenity=shelter is not suitable since the WALDHÜTTE offers no real shelter as it is - most often - a closed building. There may be WALDHÜTTEN that contain a part intended as shelter or are open to everyone, but most of them are not.