This is a gallery post and it’s being used in slider mode. Your theme comes with built-in slider / gallery plugin and allows to create unlimited sliders. Gallery post provides a selectbox that you can assign a slider / gallery to the post. That being said, same slider can be used on different pages.

This is gallery post. Your theme comes with built-in slider / gallery plugin and allows to create unlimited sliders. Gallery post provides a selectbox that you can assign a slider / gallery to the post. That being said, same slider can be used on different pages.