java swing, necessary calls in main method

java swing, necessary calls in main method

When studying for an exam I stumbled upon some lines in java graphics that
aren't really clear to me. So i started to glance and check some other
programs and they were without those lines.
example:
public static void main(String[] args){
SwingUtilities.invokeLater(new Runnable(){//unknown
public void run(){ //lines
JPanel panel = new DrawingPanel();
...
}
now i know that Runnable and run have to deal with threads, but i don't
know why and how do these two lines work