What is the difference between a complaint and a guarantee?

We are always entitled to a complaint when we buy something as consumers, while a guarantee is an additional and voluntary commitment by the seller, producer or importer that they will, for example, fix a thing that has broken. The exact conditions of guarantee (length, reasons entitiling to it, etc. are stipulated in the guarantee document). If you have a guarantee, you can still make a complaint. The choice whether to use your right to complaint or the guarantee is yours.