Most of the artificial intelligence (AI) that we currently possess or develop is capable of doing only a single task, such as playing a game of Go or driving a car. This is called narrow AI. An AI trained to play a game of Go may outperform even an expert at this game, but it cannot drive a car. Such narrow AI is not an existential risk.
Nearly all AI academics expect that a different type of AI will become available in the future: artificial general intelligence (AGI). This type of AI, which does not exist yet, could do all tasks at least as well as humans can. Opposed to narrow AI, AGI could become an existential risk. Experts believe¹ there is a 50% chance that AGI will become available by 2040-2050, and a 90% chance by 2075.