can someone explain to me and give an example of an argument being used?

An argument, also known as a parameter, is used in functions when you want to use a variable in a function, usually because you don't know exactly what you want to do or you don't know what you are performing the action. For example, say I had a function to change the BrickColor of a part:

function changeBrickColor(part, newColor)
    part.BrickColor = newColor
end

'part' and 'newColor' are the arguments, because they tell us which part to change the BrickColor of, and what to change it to. We would then call the function like so:

changeBrickColor(Workspace.Part, BrickColor.new('Really red'))

Which would change the BrickColor of Workspace.Part to 'Really red'.