A positive linear functional is like a grown-up way of saying that something is really useful and helpful. It's like when you have a toy that you really like and it brings you joy and happiness.
Now imagine if you had a toy that not only brought you joy and happiness, but it could also help you do things like clean up your room or organize your toys. That toy would be a positive linear functional.
In grown-up terms, positive linear functional refers to a mathematical concept where you can take a collection of objects (like numbers or functions) and assign a value to them that tells you how useful or helpful they are. Just like our toy, these objects can be helpful in many different ways, like helping you solve a math problem or make predictions about the weather.
To be a positive linear functional, this assignment of values has to follow some specific rules. For example, the value assigned to a combination of objects (like adding or multiplying them together) has to be the same as the combination of the individual values assigned to each object. In other words, the assignment of values has to play nicely with math.
So, to sum it up, a positive linear functional is like a really awesome toy that is both fun and helpful, and in grown-up terms, it means assigning values to mathematical objects that are useful and follow some specific rules.