Sentiment analysis is the process of identifying and categorizing emotions expressed in text, playing a crucial role in understanding public opinion and customer feedback. It employs techniques such as lexicon-based, machine learning, and deep learning, each with its strengths and weaknesses, and is widely used in marketing, politics, and healthcare despite facing challenges like sarcasm detection and contextual understanding. As technology evolves, sentiment analysis is expected to enhance its accuracy and expand its applications for more informed decision-making.