Young Blonde Girl In The Room With A Chair Posing At The Door

A garden door is any door that opens to a garden or backyard. It is often used specifically for double French doors in place of a sliding glass door (also known as Patio doors). In such a configuration, it has the advantage of a very large opening for moving large objects in and out.
A pet door (also known as a dog door or cat flap) is an opening in a door to allow pets to enter and exit without the main door being opened. It may be simply covered by a rubber flap or it may be an actual door hinged on the top that the pet can push through. Pet doors may be mounted in a sliding glass door as a new (permanent or temporary) panel. Pet doors may be unidirectional, only allowing pets to exit. Pet doors may be electronic, only allowing pets with a special electronic tag to enter.