What does this mean? "Script is not a valid member of local script

I tried to make a fireball and watched a tutorial on youtube but when i do the exact same thing he does it says to me that: *Script is not a valid member of local script

pls help

The meaning of this is basically saying that there is no script inside a local script inside your explorer.

Check that there is supposed to be a script inside of a local script using the tutorial you used. If there is then drag the script inside of the local script.

Without a view of your game's hierarchy, I can only take an educated guess at what your problem is. If you ever run into Child is not a valid member of Instance, that error message means that your script is trying to reference a nonexistent child of a given instance. From this knowledge, it is safe to assume that somewhere within your code, you have this:

script.Script

Or maybe something like this:

player.PlayerScripts['local script'].Script

Where that "Script" doesn't actually exist.