When it has a subject, verb, punctuation, capitalization, a predicate, and a complete thought. A sentence is a sentence when it is handed down by a judge (or a magistrate).
A great example of this can be when there is a football team, the coach who is there who has to be over the age of 18, should be on look out for things as bad tackles playing quality. a great one to...
It means "in place of the parents." It's usually a legal term used when a separate entity takes control of a minor--that entity is taking the place of the parents.