Help with Understanding Posts in Catgories

Hi There to all… thank u for your time.. I am new and i have gone thru the older and searches.. So fo.. no go on what i need to find out..

so hopefully some one has time to direct me here..

I have numerous child categories and I was wondering is there something plugin/widget that will not show all posts of the childrens unless i navigate to it..

I dont want to see all posting basically when i click on the parent..

Hopefully this is a simple answer and that i can limit the post from showing unless i am in the category

cheers