Many had the status of ceorls from which we get 'churl'. Not all theows, þeowne, from which we get thrall, worked on the land however and there were many categories: esne; góp; hláfbrytta, a slave in bread store; lytle, a female maid servant; scylcen, a female slave concubine and others with specific tasks such as grinding slaves. Some were born into slavery, some purchased and some penally enslaved. They did many different jobs and the use of 'chains' was epigrammtic and I am sorry if you did not understand that. Anglo saxons could be slaves too. They were not exclusively britons by any means. Serf however, is french, from latin servum, and refers to the lowest class of cultivators of the soil. It enters english well after the anglo saxons and they are not slaves. They had rights over land and property and the lord could not sell them.I wrote not "all" but "most were enslaved ". Landed slavery does not mean they were wearing chains. We might point out serfdom, in part, developed from the concept of 'slavery' or 'thralldom'.