At common law, a mortgage was a conveyance of land that on its face was absolute and conveyed a fee simple estate, but which was in fact conditional, and would be of no effect if certain conditions were not met --- usually, but not necessarily, the repayment of a debt to the original landowner. Hence the word "mortgage," Law French for "dead pledge;" that is, it was absolute in form, and unlike a "live gage", was not conditionally dependent on its repayment solely from raising and selling crops or livestock, or of simply giving the fruits of crops and livestock coming from the land that was mortgaged. The mortgage debt remained in effect whether or not the land could successfully produce enough income to repay the debt. In theory, a mortgage required no further steps to be taken by the creditor, such as acceptance of crops and livestock, for repayment.
The difficulty with this arrangement was that the lender was absolute owner of the property and could sell it, or refuse to reconvey it to the borrower, who was in a weak position. Increasingly the courts of equity began to protect the borrower's interests, so that a borrower came to have an absolute right to insist on reconveyance on redemption. This right of the borrower is known as the "equity of redemption".
This arrangement, whereby the mortgagee (the lender) was on theory the absolute owner, but in practice had few of the practical rights of ownership, was seen in many jurisdictions as being awkwardly artificial. By statute the common law position was altered so that the mortgagor would retain ownership, but the mortgagee's rights, such as foreclosure, the power of sale and the right to take possession would be protected.
In the United States, those states that have reformed the nature of mortgages in this way are known as lien states. A similar effect was achieved in England and Wales by the Law of Property Act 1925, which abolished mortgages by the conveyance of a fee simple.