This is more difficult to answer than you would expect. Many experts will provide a definition as one of the well-known beliefs. What we will do here is give you an explanation of how a manorial lordship was first used and how it has evolved over the ages.
We first must make it clear that a lordship has not always been called that, being first created by the Romans as a method of collecting taxes from the Roman villas in Britain. The lord would be the person responsible for providing the taxes for a given area of land in Britain, not necessarily all owned by him but under his authority. This system ran from just after Christ although we cannot be certain as records are thin. It is easy to find a Roman coin or piece of pottery however finding paperwork that survives that identifies their taxation system 2,000 years ago is far more difficult.
After the Romans left Britain the Saxons took over. It is assumed, based on evidence found, that the Saxons were no-where near as good administrators as the Romans and they adopted the Roman system and areas of Britain. Although we cannot see a full map of Britain showing what would have been manorial estates at this time, there are examples where names of places date back from the Domesday entry back to a Roman villa. Not only were the estates kept approximately the same but also the method of administration. A key figure in an area would be nominated as the person responsible for tax collection from his own coffers but also for all other land owners in the area designated as a single unit.
As we know from the Domesday Books the change-over of lords and taxable estates were defined as pre-Conquest and post-Conquest. It can therefore be assumed that a lordship in Saxon times as confirmed by the Domesday records might well have been a lordship in Roman times. The new Norman Lord would be responsible to the Crown for the taxation of the estate, now called a manor, in the same way as their Saxon predecessors and the Romans. The Normans were far more sophisticated than the Saxons. William wishing to reward his supporters who had assisted with the Conquest, far fewer lords were appointed than previously with some Norman lords holding many lordships each. In order to manage large numbers of manors the lords would tenant the manor to another for their life, and then to their heirs. This would create a junior lord and an overlord. The responsibility still remains the same, as in the lord of the manor was responsible for collecting the taxes, passing them to his overlord who in turn passed them to the Crown.