We come from wood and say "where you break an egg, you get a chip". It is similar in the kitchen. Wherever cooking takes place, steam is generated, grease splashes, aggressive cleaning agents are used, and sometimes things that should not leak out spill out.
To prevent all this from running down behind the worktop, the joint between the wall and the worktop must be covered with "WAPs", wall connection profiles. These are available in various sizes and different decors, which are ideally a replica of the decor on the worktop so that the moulding is as unobtrusive as possible.
All mouldings have sealing lips that press firmly against the wall during installation and prevent grease, moisture or dirt from penetrating into the joint behind. The surfaces are equipped so that they can be cleaned easily and can withstand this in the long term.