All MarblePics photos are offered under one of the following licenses depending on the photo use:
If you are NOT a MarblePics competitor (i. e. you will NOT use the photos on a photo sharing or stock photo website like this one) this license applies to you.
You can download the photos for free and use them for personal, commercial or editorial purposes without asking the author's permission. No attribution is required (i. e. you do not need to link back to MarblePics.com nor mention the photo source in any other way).
The CC BY-SA license applies to using MarblePics.com images on the photo sharing or other stock photo websites, in other words on websites like this one.
The difference between CC0 and CC BY-SA license consists in the attribution requirement. You can still download the photos for free but the attribution is required. When you redistribute the MarblePics.com photos you have to do it under CC BY-SA license.