When you purchase products in Denmark, you might find that a guarantee comes with the product that you purchase. There will often be a manufacturer's guarantee from the manufacturer, but some sellers may also offer a guarantee, for example on a second-hand car.
A guarantee is not the same as the two-year legal warranty which you have vis-à-vis the seller under Danish law. A guarantee is something more which you receive in addition to the legal warranty and can be issued by either the seller or the manufacturer. For example, there could be a five-year guarantee on your new watch, so you can make a complaint about a fault on the watch for five years.
The company is free to decide whether or not to offer you a guarantee. Therefore, the company itself largely determines the conditions of the guarantee, for example how long the guarantee lasts and what faults it covers.
The guarantee does not replace the statutory two-year legal warranty. Therefore, if a fault on the product appears in the first two years after purchase, first of all check whether the fault is covered by the legal warranty.