Heurigen are commercial restaurants run by big families or companies opened every day, usually associated with wineries and vineyards. Some of them offer more or less tasteful food and wine. One can order from either a menu or a buffet from an assortment of Austrian and Viennese specialities. On some nights there is local entertainment. Especially in Grinzing these Heurigen are very touristy and sometimes very crowded. Busses bring a load of tourists that will be seated in one of the many rooms of these deceptively large Heurigen.
The so-called Buschenschanks are rustic, inn-like places with one or two rooms and a garden, run by a local winegrower. The name points to the typical bundle of twigs (Buschen) that can be found at the entrance. The bandle signals that the Buschenschank is open, welcoming people to enter. They are opened only for some days or weeks - maybe five or sixtimes a year. There are some restrictions by law - they only can serve home-made wine, juices and cold food etc.
It's a pity that there only few traditional Buschenschanks in Vienna.
If you want to find one and to check out if opened, visit this homepage: