What is the Landing Obligation?

At the beginning of the decade, the fact that 1.7 million tonnes of fish were being discarded at sea every year in European waters was brought to the forefront of public and policy discussion. This figure shocked the European public and sparked a petition that gathered 870,000 signatures in support of a policy change to prevent discarding. The EU responded by introducing the Landing Obligation. What does this piece of legislation mean for UK fisheries?