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.

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moowoo9@fastmail.fm