En réponse à Plentyn.

The French law permit to people who donate to associations a tax reduction... So they mean that if you donate 100€, the tax which you have to pay is 66€ less elevated...
For example, if you have to pay a tax 200€, you can donate to associations 100€, and now you have to pay the tax 134€...
I don't know how it works if you're German, sorry.
I hope you've understood, I'm not really good at English...