A political party is just a group of people who agree on most critical issues and want to push forward initiatives to help resolve those issues in the electoral process and through direct action. It is important to make sure you're aligned with a political party whose platform is one that you can support, and who does not take corporate money.  Corporate money will always taint the purpose of any party.

People that come together with common goals form a Party

In the United States there are 2 main parties (Democrats and Republicans) but because both of these parties are capitalist parties, and receive money from the exact same corporations and capitalists they're mostly ran by the same agenda. Pursuing as much profit for the corporations and capitalists as possible. Don't feel you have to vote for a misogynist bigot that only represents corporations, you do not!

There are other much better political parties to belong to such as the Green Party, the Party for Socialism and Liberation, Socialist Party of America, Socialist Alternative, the Socialist Workers Party, and Peace and Freedom Party. We do most of our organizing with the Green Party and the PSL.

The logic above is often used to dissuade people from voting 3rd party.