ELI5: Explain Like I'm 5

Gelfand–Naimark–Segal construction

Okay, so imagine you have a toy box with a bunch of toys inside. Just like how the toy box can hold many different toys, a mathematical object called an algebra can hold many different mathematical operations.

The Gelfand-Naimark-Segal construction is a fancy way of creating a special kind of algebra called a *C*-algebra. These *C*-algebras are special because they have extra properties that help us understand how different mathematical operations work together.

To make a *C*-algebra, we start with a special kind of collection of numbers called a *commutative*-algebra. This means that if we multiply two numbers together, it doesn't matter which order we do it in.

Then, we use a special trick to turn this commutative algebra into a *C*-algebra. This trick involves looking at all of the different ways we can represent the numbers in the commutative algebra using functions. We call these functions "states."

By looking at all of these different functions, we can create a bigger, more complicated algebra that has all of the same operations as the original commutative algebra, but also has a bunch of extra properties that help us understand mathematical operations better.

So to summarize: The Gelfand-Naimark-Segal construction is a way of taking a commutative algebra and turning it into a special kind of algebra called a *C*-algebra, which has extra properties that help us understand mathematical operations better.