OK what on earth does this mean?

1

So I was using a handy dandy tutorial that I’d found and I came across A double equals sign ==


if (numPoints **[COLOR=Black]==[/COLOR]** 0) { 
        point1.x = evt.localX;
        point1.y = evt.localY;
        drawBoard.addChild(point1); 
        numPoints = 1;

it was used like that to create a drawing board for other objects to be drawn.

also what do the ++, +=, and -= mean?
thank you in advance