A secondary image is being used along with featured image in order to create a hover effect. Featured image appears above the entire post on posts page and above the content on single post page. Featured image alignment can be changed from Theme Options.

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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.

Image source http://nordes.by