Typically made of metal or plastic, a strainer is a mesh or sieve used to separate solids from liquid. Strainers come in a variety of sizes and shapes. Which one to use depends on what kind of items you are trying to separate. A stainless steel strainer with a fine mesh might be used to remove small pieces of seed or spices used to flavor a beverage, while a larger plastic strainer might be used to a drain water from cooked pasta.