Hello World

printfn "Hello, World!" // Output: Hello, World!

Let’s break this down:

1. printfn: This is a built-in function in F# for outputting formatted text. The printfn function is similar to printf in other languages like C, but it automatically includes a newline character at the end. It’s used here to print text to the console.
2. "Hello, World!": This is a string of characters enclosed in double quotes. It’s the argument that printfn receives, and it determines what text to print. In this case, the text to be printed is “Hello, World!”.
3. // Output: Hello, World!: This is a single line comment in F#. The F# compiler ignores anything after the // on the same line. It is often used to provide explanations or annotations about the code. Here it is used to indicate the output of the printfn line of code. This will not be printed; it’s simply a note for people reading the code.

So, to summarise, this line of F# code is a simple command to print the string “Hello, World!” to the console, followed by a comment that explains the expected output.