It is a bowl-shaped mesh metal strainer with a support handle on one end. In some traditional models, the support handle continues across the top of the mesh bowl, through the centre. Through it, is the “food mill” part, a crank handle that you turn.
Below the support handle, rubbing against the mesh, is a presser that gets turned with the crank handle. As you turn it, soft food items get pressed through the mesh or screen. The model pictured on this page comes with interchangeable screens providing varying degrees of fineness.
Passoires à coulis can be made of stainless steel, or plastic. Most come apart to make clean-up easier.
Sometimes in English you will see it described as a food mill with a steel mesh bowl.
“Passoire à coulis” means roughly “strainer for berry sauce.”
In English, this is referred to simply as a “passoire.” That doesn’t work in French, however, because any kind of strainer or colander even is a “passoire.” CooksInfo is using the term “passoire à coulis” not out of any preciousness, but rather to aid in distinguishing this from other passoires as well.