What is the purpose of the passive (non-capturing) group in a Javascript regex?

Question

What is the purpose of the passive group in a Javascript regex?

The passive group is prefaced by a question mark colon: (?:group)

In other words

Answer 1

When you want to apply modifiers to the group.

/hello (?:world)?/
/hello (?:world)*/
/hello (?:world)+/
/hello (?:world){3,6}/

etc.