Artificial Intelligence is the study of intelligence in algorithms. On LessWrong, discussion of AI is focused on AI Alignment, to ensure that as humanity builds increasingly powerful AI systems, the outcome will be good. The central concern is that a powerful enough AI, if not designed and implemented with sufficient understanding, would optimize something unintended by its creators and pose an existential threat to the future of humanity.
Common terms in this space are superintelligence, AI Alignment, AI Safety, Friendly AI, Transformative AI, human-level-intelligence, AI Governance, and Beneficial AI. This entry and the associated tag roughly encompass all of these topics: anything part of the broad cluster of understanding AI and its future impacts on our civilization deserves this tag.