You might decide that the size of the house is A and the price of the house is B, and have an AI system learn this input to output or A to B mapping. Now, rather than just pricing a house based on the size, you might say, well, let's also collect data on the number of bedrooms of this house. In that case, A can be both of these first two columns, and B can be just the price of the house. So given a table of data, given a data set, it's actually up to you, up to your business use case to decide what is A and what is B. Data is often unique to your business. And this is an example of a data set that a real estate agency might have if they're trying to help price houses. And it's up to you to decide, what is A and what is B, and how to choose these definitions of A and B to make it valuable for your business.