CFD Online Discussion Forums - what does the function min() do???

Somewhere in the source Code of a turbulence model I found something which I dont understand. Unfortunately the understanding of this line is crucial to what I am doing. The line I am talking about is

Code:

P[faceCelli] *=

                    min(G[faceCelli]/(0.5*mag(tr(P[faceCelli])) + SMALL), 1.0);

What I dont understand are the following things:

what is SMALL? A variable a function??
what does the function min do? Does it select eitherG[faceCelli]/(0.5*mag(tr(P[faceCelli])) + SMALL) or 1.0, depending on which value is the smaller one

If I do some more source Code searching, I find

Code:

inline retType min(const type1 s1, const type2 s2) \

{                                                  \

    return (s1 < s2)? s1: s2;                      \

}

Can someone understand this?

Thank you very much!