Advocacy is the act of arguing on behalf of a particular issue, idea, person or animal. An advocate is someone who does this. Both the terms advocate and advocacy have specialist meanings in certain contexts, and among some groups. For instance:
In a legal/law context: An 'advocate' is the title of a specific person who is authorised/appointed (in some way) to speak on behalf of a person in a legal process. See advocate. An advocate is one who speaks on behalf of another person especially in a legal context
In a political context: An 'advocacy group' is an organized collection of people who seek to influence political decisions and policy, without seeking election to public office. See interest group. An interest group (also advocacy group, lobby group, pressure group or special interest group) is an organized collection of people who seek
In a social care context: Both terms (and more specific ones such as 'independent advocacy') are used in the UK in the context of a network of interconnected organisations and projects which seek to benefit people who are in difficulty (primarily in the context of disability and mental health).
In the context of inclusion: Citizen Advocacy organisations (citizen advocacy programmes) seek to cause benefit by reconnecting people who have become isolated. Their practice was defined in two key documents: CAPE, and Learning from Citizen Advocacy Programs. See Citizen Advocacy organisations. ' Citizen Advocacy organisations' (Citizen Advocacy programs/programmes seek to cause benefit by reconnecting people who have become isolated from the ordinary community
In a marketing context: The word advocate is used to describe a loyal client that recommends a product or service to their peers.