Simple

Here follows a (short) description of both.

Mandolin: a musical instrument in the lute family. Mandolins evolved from the lute family in Italy during the seventeenth and eighteenth centuries, and the deep bowled mandolin, produced particularly in Naples, became common in the nineteenth century. The original instrument was the mandore, which evolved in the fourteenth century from the lute. As time passed and the instrument spread around Europe, it took on many names and various structural characteristics.

Mandoline: a cooking utensil used for slicing and for cutting juliennes; with proper attachments, it can make crinkle-cuts. It consists of two parallel working surfaces, one of which can be adjusted in height. A food item is slid along the adjustable surface until it reaches a blade mounted on the fixed surface, slicing it and letting it fall.

With a mandoline, slices are uniform in thickness, which is important with foods that are deep-fried or baked (e.g. potato chips), as well as for presentation. Slices can be very thin, and be made very quickly, with significantly less skill and effort than would be required if cutting with a knife or other blade.