What does this function do?

[infringement153]

Clicking "auto system" when you've selected multiple things at once--what does it do? 

Also, what's the difference between clicking "binary orbit" and "orbit parent"?

Also, if somebody happens to have time to kill, could they please be helpful and instruct me how to...

~Make a small star
~Make two large planets orbit each other, the barycenter of which orbits around the star
~Make another planet orbit the barycenter of the three bodies.

Thank you. 

[atomic7732]

1. Place a star, change the mass and radius down alot.
2. select the two planets. click binary orbit.
3. I don't think you can do that...

[Naru523]

Also, what's the difference between clicking "binary orbit" and "orbit parent"?

Binary orbit does the same thing as orbit parent, but much more accurate.

3. I don't think you can do that...

The third one is possible to do.

[atomic7732]

Binary orbit does the same thing as orbit parent, but much more accurate.

No... What it does is orbits the object, but regardless of masses. So you can orbit any masses. If you use orbit parent, if you try to make a more masseous object orbit a smaller mass... Then it wont work, also low ratios (1:2, 1:3) seem to give odd orbits using orbit parent.