This is a German tax phenomenon, not a financial accounting concept, but of course it appears in German financial accounts as well because of the principle of "umgekehrte Maßgeblichkeit" (tax dictates financial accounting).

The correct technical term (in the EStG) is actually "Ansparabschreibungen", but these are generally referred to collectively as the Ansparrücklage. There are actually quite strict terms attached to the eligibility to recognise this particular type of reserve, for example it may only be used for moveable assets, and the nature and cost of the assets in question must be defined in advance.

There are two main occurrences of the Ansparrücklage. The first is for start-ups, which are allowed generous investment reserves stretching over quite a long period (six years I think). The second (and more common) is for small businesses, incl. freelance translators, which are allowed a smaller amount and are restricted to a shorter period (2 years). Any portion of the investment reserve that goes unused is recycled to taxable profit.

The Ansparrücklage is also frequently referred to as the Investitionsrücklage in the literature.