If this parameter is set to YES
If you have Activities this way
A1 - recorded
A1.1 - recorded
A1.2 - recorded
When first sub-activity moves to "in progress", parent also moves to is progress
A1 - in progress => changed automatically
A1.1 - in progress => changed manually
A1.2 - recorded
When last sub-activity moves to done status, parent also moves to done status
A1 - done => changed automatically
A1.1 - done => changed manually
A1.2 - rdone => changed manually

Really good option !!
Could you please tell me if it works with activity as mother and link ticket as child for example?
Or with Meeting as mother and linked ticket as child ?
Or with Action as mother and linked ticket as child ?

Thanks

Could you please tell me if it works with activity as mother and link ticket as child for example?

No

Or with Meeting as mother and linked ticket as child ?

No

Or with Action as mother and linked ticket as child ?

No

It only works with "planable" items (items displayed on Gantt chart)