What is Artificial Intelligence? (AI)

Bring up Artificial Intelligence in a room and people's minds wander to shiny robots who will take our jobs or a lot of science fiction. If we look at the Oxford dictionary definition of Artificial Intelligence, this is what we get: 'the study and development of computer systems that can copy intelligent human behaviour.' For the majority of society, this means very little, however if you work or are surrounded in the tech industry, you have our personal definitions. The limitation of the definition that Artificial Intelligence is primarily based on computers imitating human intelligence does not give us a broad understanding of what Artificial Intelligence actually is? What's the difference between types of AI? What type of AI is Siri?