Access structures are used in the study of security systems where multiple parties need to work together to obtain a resource.
Less formally it is a description of who needs to cooperate with whom in order to access the resource.
In its original use in cryptography, the resource was a secret shared among the participants.
[2] Only subgroups of participants contained in the access structure are able to join their shares to recompute the secret.
More generally, the resource can also be a task that a group of people can complete together, such as creating a digital signature, or decrypting an encrypted message.