"Child of" versus "is Child of"

[jeroen.wilmes]

When creating a link a have a.o. a choice between "child of" and "is Child of". 
What is the difference between the two?
The same question for "Parent of" and "is Parent of"

[Nic Brough -Adaptavist-]

Nothing really.

I'd suggest asking your admins why they've added duplicate issue link types!

[Claire Berry]

Hi, we have the same issue, I suspect it was created from some plugin