Critical thinking is self-directed thinking that involves analyzing and assessing arguments and information to improve one's thinking. It involves skills like raising vital questions, gathering and assessing relevant information, and coming to well-reasoned conclusions. Critical thinking is important for problem solving, decision making, understanding complex systems, and identifying different perspectives. It plays a key role in the 21st century by helping people question assumptions, think flexibly, make good decisions, and address problems through in-depth analysis. The document emphasizes that critical thinking skills are essential for lifelong learning and success.