Smart software, not a robot
When people say "AI", they often picture a robot. Forget the robot. AI is software: a program running on ordinary computers, often in a data centre far away. The name is short for artificial intelligence, a term the computer scientist John McCarthy coined in 1955. It covers any program that does something we would call smart. That usually means one of three jobs. Recognising things, like your face or your voice. Predicting things, like the next song you will want. Or generating things, like a new picture or a paragraph of text. Your phone does all three every day.
Two ways to make a computer smart
There are two ways to build smart software. The old way is to write rules by hand. A programmer types out every step: if the email contains this phrase, mark it as spam. Rules work well for simple, clear jobs, like calculating a bill. But try writing rules for spotting a cat in a photo. Cats come in every colour, pose and lighting. You would never finish. The new way is called machine learning. Instead of writing rules, you show the computer thousands of examples and let it work out the pattern itself. Almost every AI you use today was built this way.
How you recognise a friend
Think about how you spot a friend in a crowd. You could not write down the rules. You cannot say exactly what makes their face theirs. Yet you know them instantly, from behind, in bad light, with a new haircut. That is because you have seen them thousands of times, and your brain learned the pattern. Machine learning works the same way. Nobody writes the rules for "cat". The computer sees enough cats that the pattern sinks in.
Four ideas that nest inside each other
- Artificial intelligence is the biggest circle: any software that does something we would call smart, whether it was hand-coded or learned.
- Machine learning sits inside it: software that learns its own rules from examples. Deep learning sits inside that: machine learning done with a neural network, a model built from layers of tiny calculations.
- Generative AI is the newest and smallest circle: deep learning that makes new things, such as text, images and sound. ChatGPT lives here.
What comes next
Almost everything else about AI follows from one question: how does a computer learn from examples? Not by memorising them, and not by reading a rulebook. The next lesson shows the simple loop that does it, and why it has to be repeated millions of times.
Check yourself · 3 quick questions
Which is the best description of AI?
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Software that does things we would call smart — AI is software, not a robot: any program that recognises, predicts or generates something we would call smart.
What is the main difference between rule-based software and machine learning?
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Rules are written by a person; machine learning finds the pattern from examples — With rules, a programmer types out every step; with machine learning, the computer works out the pattern from many examples.
Which of these is the biggest circle, containing all the others?
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Artificial intelligence — Artificial intelligence is the widest idea; machine learning, deep learning and generative AI each sit inside the one before.