"Unable to cast string to int" error - what?

So I'm working on a GUI that teleports you to games I've made, although an "Unable to cast string to int" error always comes up in the output when I edit a particular line in my code:

function onClicked(mouse)
	print("Teleport Script Loaded")
	wait (1)
	game:FindService("TeleportService"):Teleport("id")
	wait (1)
	print ("Teleport Script Successful")
	wait (1)
end

script.Parent.MouseButton1Click:connect(onClicked)

I know it's something to do with line 4 because it manages to print "Teleport Script Loaded" but never gets past that, also it says that there's an issue with line 4 in the output.

Any ideas on what's going on?

Remove the quotes around id.

It is expecting a number, you are providing a string. If ID is a variable, it is also not being used. the literal string, "id" is.

As you can see here Teleport, from TeleportService, expects an int.

What the error is saying is that it is unable to use the string, and an int(a number) is expected.

Differences:

-- This is a number. it is valid.
number = 12345
-- This is not a number. It contains characters other than 0-9 or math functions (such as "*", "/", "+", "-")
notANumber = 1234a
-- This is a string. It is valid. It is different from number. it can be converted to a number by using tonumber(str)
str = "12345"
-- This is still a string. It can not be converted into a number using tonumber() because It contains characters other than 0-9 or math functions
stillAString = "1234a"

That error message means you are trying to use a string value for something that requires a number.

In your case, you tried to teleport a player to a place whose ID is "id," instead of something like 123456789. Just remove the quotes around the "id" on line 4.

Thanks for the answers, guys. But I forgot to say that there was a number value in the TextButton that I was using to launch the game, in which buttons that display details of the game in a GUI would also change the value to the place Id.

This is what I ended up with, if anyone wants to use it for their own game:

id = script.Parent.PlaceId.Value

function onClicked(mouse)
	print("Teleport Script Loaded")
	wait (1)
	game:FindService("TeleportService"):Teleport(id)
	wait (1)
	print ("Teleport Script Successful")
	wait (1)
end

script.Parent.MouseButton1Click:connect(onClicked)

Thanks again for the help!