In legal terms, concealment refers to hiding something which should be revealed. It can take a number of different forms, some of which have legal consequences. Concealment can be prosecuted if it can be demonstrated that harm was caused by the activity because one party was not operating with all of the facts. It is possible to engage in concealment by accident, by not realizing that a fact should have been disclosed, but this is sometimes treated like intentional concealment in the eyes of the law.
In contract law, concealing information can void the contract, depending on the nature of the concealed information. The general rule is that people are required to reveal information which could be relevant to the contract at the time that the contract is written. For example, someone applying for car insurance must disclose driving history to the insurer. If the facts would have caused one party to proceed differently had they been known, this will be considered concealment, as for example if someone failed to disclose a series of accidents to a car insurance company.
People may also use this term to refer to a form of theft. If someone conceals merchandise on the body while in a store, there may be reasonable belief that the person intended to steal. Even if the merchandise has not been carried out of the store, the concealment can be used as evidence that the person was not planning on paying. People can be prosecuted for theft in such situations.
Both active and passive concealment can be seen. In the case of active concealment, active steps are taken to make sure that facts are not uncovered. For example, a real estate agent could remove a disclosure page from a packet of information about a property so that the prospective buyer would not see the information on that page. In passive concealment, someone fails to speak when it would be reasonable to do so. To borrow the real estate example again, if a real estate agent knows about a defect with a property and does not disclose it, this could be grounds for suit.
A related concept is a concealed weapon. By law in many regions of the world, people who carry weapons must do so openly, and additional laws usually apply to the types of weapons which can be carried. However, there are special circumstances in which people can apply for a concealed weapon permit, if they can demonstrate that concealment is necessary for safety. The permit applies to a specific weapon and can be revoked if there is a belief that it is no longer necessary or it is being used inappropriately.