What is Critical Thinking?
Critical thinking is the analysis of facts to form a judgment . To elaborate, critical thinking is to examine every piece of fact and/or evidence that is available BEFORE you make a decision about a topic. We, as humans, have a very hard time of practicing it on a daily basis. It takes PRACTICE and DISCIPLINE. The hardest part of critical thinking is taking the emotions out of the decision you make based on the facts you have evaluated.
Critical thinking is self-directed, self-disciplined, self-monitored, and self-corrective thinking . This means, you also need to develop those skills as part of critical thinking. Here are the definitions:
Self-directed: A process in which individuals take the initiative, with or without the help of others, in diagnosing their learning needs, formulating learning goals, identifying human and material resources for learning, choosing and implementing appropriate learning strategies, and evaluating learning outcomes .
Self-disciplined: The ability to control one's feelings and overcome one's weaknesses; the ability to pursue what one thinks is right despite temptations to abandon it.
Self- monitored: The ability to both observe and evaluate one's behavior.
Self-corrective thinking: The ability to change your mind from the original (many times emotional) judgement.
Why do you need to learn this?
Critical thinking is individual thinking. Almost every historical leader have shown signs of critical thinking. Before we go into the subject of Civics/History, we need this foundation. According to a survey from Payscale, 60% of college GRADUATES do not have critical thinking skills and that is a major problem. Therefore, this skill is something that will be valued in ANY career you choose! 
 Edward M. Glaser. "Defining Critical Thinking". The International Center for the Assessment of Higher Order Thinking (ICAT, US)/Critical Thinking Community. Retrieved 22 March 2017.
 Clarke, John (2019). Critical Dialogues: Thinking Together in Turbulent Times. Bristol: Policy Press. p. 6. ISBN 978-1-4473-5097-2.
 Knowles, M. (1975) , New York: Cambridge Books.