Artificial Intelligence (AI) refers to the simulation of human intelligence in machines that are programmed to think like a human and mimic their actions. The term may also be applied to any machine that exhibits traits associated with a human mind such as learning and problem-solving.

AI can be categorized into two main types:

1. Narrow AI: Also known as Weak AI, this type of artificial intelligence operates under a limited pre-defined range or set of contexts. It’s designed and trained for a specific task. For example, virtual personal assistants, such as Siri or Alexa, are forms of narrow AI.
2. General AI: Also known as Strong AI, this AI would have the understanding, consciousness, and intelligence of a human being. It would be able to understand, learn, and apply knowledge in different domains, reason through problems, have consciousness, and even have emotional understanding. General AI remains a largely theoretical concept and has not been achieved yet.

AI technologies include machine learning, where computers are trained to learn from input and get better over time. Neural networks, deep learning, natural language processing, and computer vision are other essential technologies in AI.

Applications of AI are numerous and growing, with examples in areas like healthcare (for diagnosis and personalized treatment), transportation (in self-driving cars), finance (for fraud detection and robo-advisors), entertainment (for game design and movie recommendations), and many others.

The development and deployment of AI raise several ethical and philosophical questions, including issues related to bias, job displacement, security, and the potential misuse of highly advanced AI systems. These concerns have led to ongoing debates about regulations and the responsible development of AI technologies.