[Haskell-beginners] code explanation

[moowoo9 at fastmail.fm]

I'm a beginner, I'd like someone to help me understand a few
lines of code
My questions are:
1) Maybe String is an application of the constructor Maybe to the
type String.
What does it mean? Is there anything equivalent in the C
language?
2) Is this a function with three arguments?
type T = [Char]
type P = (Char, Maybe String)
type Delta = ((Maybe Char, Char), Maybe String)
fromGtoM :: T -> [P] -> [Delta]
3) is this a usage of the above mentioned function?
fromGtoM t p = terminalRules ++ varRules
I dont'see why the function has three arguments but then only
two are used t p.
4) what does ++ mean ?

Sorry, for posting too many questions.
Thanks in advance.
--

moowoo9 at fastmail.fm

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