Paper shredders are a staple in just about every office. They are mainly used to destroy reports and documents that have sensitive information printed on them. Such papers might have employee information, company financials or company plans.
If a company is not going to be keeping the data in files, they have extra copies, or they are no longer required to keep the documents; they will normally throw them away. However, if the papers have information on them that someone else could use, such as Social Security numbers, they they will want to make the papers unreadable. This is where shredders come in. They cut the paper into small pieces that become almost impossible to put back together.
Shredders have metal blocks with sharp edges inside, or sometimes blades, that are placed close together but staggered front and back. When the machine is turned on, you can feed a piece of paper into the top. The metal grabs the paper and pulls it through the shredder, cutting as it goes. The paper comes out the other end as strips.
In some more expensive models, there will be a blade that comes across the bottom, taking the strips of paper and cutting them again. This causes the paper to come out the bottom in small squares or confetti.
Most shredders come with a container that catches the paper as it comes out the other end. If not, then they usually are built so that they can be placed over a trashcan to catch the waste.
If you place a bag in the can it makes disposal easier, since the little pieces of paper can be hard to collect otherwise.