Using the stream insertion operator to read files

I happened to run across a code example for reading text from a file as follows:

int i; 
 char *fileName = "text.txt"; 
 ifstream fin(fileName); 
 
 while (fin >> i)
 {
 do something;
 }
 

This code actually opens and reads space-delimited text, but I don't understand how it works. How does the file get opened without an "open" or "read" command? Is there a way to rewind back to the beginning of the file? I'm trying to create a dynamically allocated array, which I don't know how to do until after I've counted through the file for the number of scores.

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