I'm really trying to understand the overlay position parameter but without any luck. I also can't find any documentation about this topic.

What does the following code mean?

```
const positions = [
  new ConnectionPositionPair({ originX: 'start', originY: 'bottom' }, { overlayX: 'start', overlayY: 'top' }),
  new ConnectionPositionPair({ originX: 'start', originY: 'top' }, { overlayX: 'start', overlayY: 'bottom' })
];
this.positionStrategy = this._overlay.position()
.flexibleConnectedTo(this.getConnectedElement())
.withPositions(positions)
.withFlexibleDimensions(false)
.withPush(false);

```