Secret sharing
Secret sharing (also called secret splitting) refers to methods for distributing a secret amongst a group of participants, each of whom is allocated a share of the secret. The secret can be reconstructed only when a sufficient number, of possibly different types, of shares are combined together; individual shares are of no use on their own.
In the image above, each secret share is a plane, and the secret is the point at which three shares intersect. Two shares yield only a line intersection.