A party platform is a set of guidelines that outline the policies and beliefs that a party seeks to implement. The platform is typically written by the leadership of the party that is made up of policy experts, committee heads and directors.
A party platform is typically used by a political party to appeal to the general public. A platform with sympathetic or viable opinions and viewpoints are used to garner votes and support from like-minded individuals in the population. A few prominent examples of political platforms through history include the "Ninety-Five Theses" by Martin Luther and the "Communist Manifesto."