In Germany (and countries with similar systems) the route to becoming a professor requires an additional qualification above your doctorate. This process is known as [Habilitation][1]. So a "Habilitationsstelle" is the position / job that you will do while working towards this even higher qualification. Same as a Doktorstelle is the position / job you will hold while working towards your doctorate. So yes it is postdoctoral, but not really equivalent to the way the US or UK systems work.


  [1]: https://en.wikipedia.org/wiki/Habilitation