What Is Threshold Encryption?

The idea of threshold encryption is that you have a total of N people whose public keys are in a single block. Anyone can pick out L of them and create an encryption key using their public keys from the block. Then the sender can specify a threshold T and encrypt a message which gets sent to the L recipients. If T of those recipients use their private key on the encrypted message it can be decrypted, but if not enough get together it can not be decrypted.