Which or that .- Used mainly for objects.
Where.- Used for places.
Who .- Used for people.
Whose.- Used for expressing possession.
When.- Used for expressing time.
Examples:
CEIP Punta de n'Amer is the place where I study.
A hospital is a place where people go if they are sick.
Santa Claus is the person who brings you presents at Christmas Eve.
The man who is wearing a red cap is my uncle.
The car which is old is my granny's one.
The pencil which I use, is not mine.
The boy whose jacket is green is my brother.
The house whose garden is full of flowers is Mrs Smith's one.
Summer time is when students do not go to school.
Summer time is when open-air celebrations take place.