When a landowner died leaving an under-age heir, custody of the estate during the minority could devolve upon the landowner's family or upon the lord from whom he had received the estate. The term wardship was normally used to describe the second of these situations. After the Conquest, wardship in this sense became the norm and was a politically contentious matter for centuries thereafter. Custody by the family was more common before the Conquest, though wardship in the post-Conquest sense was not unknown, as one case in Worcestershire (2,33) reveals.
For more detail, see Sir Fredrick Pollock and F.W. Maitland, The history of English law before the time of Edward I (second edition, 1898); A.L. Poole, Obligations of society in the XII and XIII centuries (1946); and Susan Reynolds, Fiefs and vassals: the medieval evidence reinterpreted (1994).