This is a crinkle cut potato slicer (sometimes called a "mandoline" or "wavy vegetable cutter") used to slice vegetables and fruits into wavy-edged pieces.
The blade is usually made of stainless steel for durability and rust resistance.
It is used to make crinkle-cut French fries or decorative cucumber and carrot slices for salads.
The slicer allows for uniform slices in shape and thickness.