A communist is a person who believes in a political and economic system [the way a country is run and how people earn money and trade goods] where everyone works together and shares everything equally.
In a communist system, there is no private ownership of property [things that people own, such as houses, land, or businesses] and the government controls all resources [things that people use to make goods or provide services, such as oil, gas, or timber]. The goal of communism is to create a society where everyone has access to the same resources and opportunities, regardless of their social class [the group of people in a society who have similar levels of money, education, or power] or background.
Overall, communism is a political and economic theory that seeks to create a fair and equal society where resources are shared equally and everyone has an equal chance to succeed.
Very Simple Definition:
A communist is someone who believes that everyone should work together and share everything equally. They think that everyone should have access to the same things, and that no one should be richer or poorer than anyone else.