    *NOTE to the author     there is a big difference between the two parties. Democrats are more liberal and Republicans are a lot more conservative.       Note to the Note   The question was related to the PARTIES, not the philosophy of individual members.
It works like this: a political party through its manifesto says-if you vote for me then I will do this for you. Uses: 1. Canvassing of vote for political parties 2. Helps people to decide which party to vote for 3.
The formal purpose of such a convention is to select the party's nominee for President, as well as to adopt a statement of party principles and goals known as the platform and adopt the rules for the party's activities, including the presidential nominating process for the next election cycle.