This is the 13286th most frequent Spanish word.
puestas
"Puestas" means "placed" or "set."
Here, 'puestas' is a participle used as an adjective indicating the arrangement or position of the chairs.
Las sillas están puestas en orden en la sala.
The chairs are arranged in order in the room.
In this context, 'puestas' is part of the noun phrase 'puestas de sol', meaning sunsets. It describes the phenomena associated with the setting of the sun.
Ellas hablaron de las puestas de sol que vieron en sus vacaciones.
They talked about the sunsets they saw on their vacation.
Here, 'puestas' is used in a reflexive construction to indicate that the action of placing the bets has been completed (passive meaning).