A sieve (or a mesh strainer) is a mesh bowl with a handle. They are commonly used to sift flour or to strain and separate solids from liquids. It can also be used to reducing soft solids into a pulp.
Sifting flour makes it easier and faster to mix it to batters and cake mixtures. It also prevents the doughs from clumping or having an uneven texture. You can use a sieve to dust a countertop evenly with flour if you need to roll out some pastry or some pizza dough.
They can also be used in decorating for cakes and desserts, simply add some cocoa or icing sugar and tap the side with your hand to create a fine dusting on top of your sweet thing.
Sives can also be used to strain food. You can pass food like soups, smoothies, and purées to get a really smooth result. A strainer is essential for making wonderfully smooth raspberry coolis. You can also squeeze citrus fruit directly into a sieve to separate the pulp and the seeds hassle free!