From the Document: "While the term 'earmark' has been used historically to describe various types of congressional spending actions, since the 110th Congress (2007-2008) House and Senate rules have defined an earmark as any congressionally directed spending, tax benefit, or tariff benefit that would benefit an entity or a specific state, locality, or congressional district. In the 112th Congress (2011-2012), the House and Senate began observing what has been referred to as an earmark moratorium or earmark ban. The moratorium does not exist in House or Senate chamber rules, however, and therefore is not enforced by points of order. Instead, the moratorium has been established by party rules and committee protocols and is enforced by chamber and committee leadership through their agenda-setting power."
CRS Report for Congress, R45429
Congressional Research Service: https://crsreports.congress.gov/