In terms of explosives and blasting:

The 'donor' is the first part of the Donor-Receptor relationship that delivers energy to the receptor.

The key factor of the donor is the amount of energy provided. This may be measured in terms of equivalent mass of TNT.

The 'receptor' is the second part of the Donor-Receptor' relationship that accepts energy from the donor and, if sensitive enough, will then detonate.

On detonation the receptor becomes the donor to the next part of the explosives chain.

The Donor-Receptor relationship may be summarised as:

For reliable propagation the output of the donor must exceed the sensitivity of the receptor.

The Donor-Receptor relationship is key to understanding propagation and failures.