This rule completely hides the output product from Mergado.
Hiding goods that are not competitive when selling on comparison engines is a way to save on costs. For example, Mergado users use it for goods that have a long delivery time. If a competitor has it in stock and for a similar price, it is difficult for the customer to buy it from you. In practice, for example, you make a selection of products with a value of DELIVERY_DATE larger than (for example) 10 and apply a hiding rule to it.
Similarly, this rule is useful when you advertise on GLAMI and there are other items besides fashion in your e-shop. By creating a selection with a different CATEGORYTEXT and its subsequent hiding you make sure that only products from the fashion category get to the search engine.