Vacuum sealing is an integral part of sous vide cooking — the name of the method itself even comes from the French for 'under vacuum'. There are two main types of vacuum sealers: bar sealers (which suck the air out of the vacuum bag) and chamber sealers.
Chamber sealers work by creating a vacuum around the bag to expel the air. Unlike bar sealers, therefore, a chamber sealer can be used to lock liquids and sauces into the bag along with the ingredients. Chamber sealers are the most commonly used type of vacuum sealer in professional kitchens.