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An 'estate in land' is an interest in land that is endowed with certain rights and obligations, and carries a right to occupy or receive the benefit of the land. As well as estates in land, there are non-proprietary interests in land, such as licences (see: Licence). There are also proprietary interests that fall short of being estates - Mortgages, Easements, Franchises, etc. It is not always easy to distinguish an estate (particularly a lease) from a lesser form of interest, and courts are often called upon to make rulings in such cases (see: Lease or licence).

Estates can be 'legal' (recognized by the common law) or equitable. Historically the common law recognized legal estates in land that were many and various. Currently, however, there are only two legal forms of estate in land, as defined in the Law Of Property Act (1925): Fee simple absolute in possession and Term of years absolute. The 'fee simple' is a form of freehold and the 'term of years' a leasehold. This means that it is now customary to use the term 'freehold' to mean the 'fee simple absolute in possession' and the term 'leasehold' to mean the 'term of years absolute'. That is, although these terms are not strictly synonymous with each other, they are often spoken of as if they were. It also follows that any form of legal (i.e., non-equitable) tenancy that may exist that is not a lease is not an estate, but a lesser interest.

Land belonging directly to the Crown is not, technically, a freehold estate in land: the term 'freehold' denotes land historically granted by the Crown to a private citizen (see demesne land of the crown for the techicalities).