Donor chains work similarly to paired kidney exchanges, in that they take advantage of willing but incompatible donors/recipient pairs. The chain is initiated by what is called a non-directed donor. A non-directed donor is someone who offers to donate their kidney without a designated recipient, but with the goal to donate to someone in need of a kidney.
Kidneys from non-directed donors are used to initiate a chain of kidney transplants for incompatible donor/recipient pairs. This could potentially include numerous incompatible pairs.