Artificial Intelligence (AI) refers to the branch of computer science dedicated to creating systems capable of performing tasks that typically require human intelligence. This encompasses a wide range of functionalities, including reasoning, learning, problem-solving, perception, natural language understanding, and decision-making.

AI systems can be classified into two main categories:
Narrow AI: Also known as weak AI, this type is designed for specific tasks, such as image recognition, language translation, or playing chess. Narrow AI operates within a limited context and cannot perform outside of its designated function.
General AI: Also referred to as strong AI, this theoretical form of AI would have the ability to understand, learn, and apply knowledge across a broad range of tasks at a level comparable to that of humans. As of now, general AI remains largely a concept and has not yet been achieved.

AI technologies utilize various methodologies, including Machine Learning (where systems learn from large data sets and improve over time), Deep Learning (which involves neural networks with many layers), and natural language processing (allowing computers to understand and generate human language).

AI has the potential to revolutionize many areas, including healthcare, finance, transportation, and entertainment, by automating tasks, enhancing decision-making, and leading to innovations that were previously unimaginable. However, it also raises ethical concerns and challenges, such as job displacement, privacy issues, and biases in decision-making algorithms, which require careful consideration and regulation as technology advances.