Java Regex Capturing Groups

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I am trying to understand this code block. In the first one, what is it we are looking for in the expression?

My understanding is that it is any character (0 or more times *) followed by any number between 0 and 9 (one or more times +) followed by any character (0 or more times *).

When this is executed the result is:

Found value: This order was placed for QT3000! OK?
Found value: This order was placed for QT300
Found value: 0

Could someone please go through this with me?

What is the advantage of using Capturing groups?

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class RegexTut3 {

    public static void main(String args[]) {
        String line = "This order was placed for QT3000! OK?"; 
        String pattern = "(.*)(\\d+)(.*)";

        // Create a Pattern object
        Pattern r = Pattern.compile(pattern);

        // Now create matcher object.
        Matcher m = r.matcher(line);

        if (m.find()) {
            System.out.println("Found value: " + m.group(0));
            System.out.println("Found value: " + m.group(1));
            System.out.println("Found value: " + m.group(2));
        } else {
            System.out.println("NO MATCH");
        }
    }

}

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