Qt signals and slots, threads, app.exec(), and related queries

[related to this question]

I wrote this piece of code to understand how qt signals and slots work. I need someone to explain the behaviour, and to tell me if I'm right about my own conclusions.

My program:

connectionhandler.h

#ifndef CONNECTIONHANDLER_H
#define CONNECTIONHANDLER_H

#include <QTcpServer>
class ConnectionHandler : public QObject
{
    Q_OBJECT
public:
    ConnectionHandler();
public slots:
    void newConn();
private:
    QTcpServer *server;
};

#endif // CONNECTIONHANDLER_H

connectionhandler.cpp

#include "connectionhandler.h"
#include <QTextStream>

ConnectionHandler::ConnectionHandler() {
    server = new QTcpServer;
    server->listen(QHostAddress::LocalHost, 8080);
    QObject::connect(server, SIGNAL(newConnection()),this, SLOT(newConn()));
}
void ConnectionHandler::newConn() {
    QTextStream out(stdout);
    out << "new kanneksan!\n";
    out.flush();
}

main.cpp

#include <QCoreApplication>
#include "connectionhandler.h"

int main(int argc, char* argv[]) {
    QCoreApplication app(argc,argv);
    ConnectionHandler handler;
    return app.exec();
}

Now, running this program sends it into an infinite loop looking for new connections.

Observation: if I don't call app.exec(), the program returns immediately (as it should).
Question: why?

Question: if I had connected the slot as a queued connection, when would the slot invocation be performed?
Question: if app.exec() is an infinite loop of sorts, how does the newConnection() signal ever get emitted?

Big Question: Is their any "second thread" involved here? (I expect a no, and a stunningly