restrictive or
non-
restrictive clauses.
These are other terms for (in)direct clauses
1. A restrictive clause takes a clause with information you can't leave out. We need the information for better understanding.
2. A non - restrictive clause takes a clause with information you can leave out.
Do you know the girl who/that sings at the Prom?
Students whose parents are rich pay extra fees.
My neighbour, whose wife is my teacher, waters the plants every day.