`Input.GetButton()` takes a `String` defining a button configured in your input manager.
If you have defined a button Inventory, then you probably wanted
Input.GetButton("Inventory")
If you want the code to only act when the button is held down, you probably wanted
Input.GetButtonDown()
If you wanted the inventory thing to only happen when the `Input.Get...` was true, then you should put it inside of an `if` statement
if(Input.GetButtonDown("Inventory"))
//show your GUI
What is `show` supposed to be? If `show` is an `enum`, `class` or class instance, then this is syntactically correct, but will not actually do anything.
What is `inventoryGui` supposed to be? If it is a variable of a class, then you should be assigning or changing it like `show.inventoryGui = something;`. If it is an `enum`, then you should be assigning something to have its value like `something = show.inventoryGui;`. If it is a function, you must call it with parentheses like `show.inventoryGui();`.