Linsensuppe refers to lentils soup, a popular soup in Germany made of lentils made of vegetables like carrots, leeks, celery as the base of the soup plus fresh herbs and spices to spice it up and the main ingredient is the lentils called Linsenbohne in German.
There are different kinds of Linsenbohnen available in German supermarkets as Linsen is also made into a stew (Linseneintopf) in Germany.