Sure, I wouldn't claim that anchors are self-explanatory

So, let's concentrate just to those four buttons.
- Top left: anchor to object. You can click an anchor to object and anchor will move with the object it's anchored.
- Top right: anchor to world. It's a static anchor and doesn't move anywhere. It doesn't collide either with anything.
- Bottom left: start anchor. If you "toggle on" start anchor the next object (like box) will be anchored. Check status line for more information. In brief: toggle on start anchor, select a box button, click an existing anchor in the world and draw a box -> box will be anchored.
- Bottom right: end anchor. Applies only for chains and pipes. Usage example: toggle start and end anchors on, select a chain box, click start anchor in the world, draw a chain and click an end anchor -> chain will be anchored from both ends.

Note: start and end anchor buttons are toggled off automatically after tool is selected.

Hope this explained the usage. You can do quite fancy things with anchored chains. Swing set, winch etc.