The shelf in the first picture is made of red oak plywood. You can choose the wood type, color and design as you like for your project. In case if you need more help understanding this project, you can refer the source link below. It discusses various items used, steps and tips and personal experience of the author who personally built a Zigzag shelf.
Pocket screws create a solid, simple-to-make joint. Because of the size and visibility of the hole, it’s usually located in areas that are concealed or rarely seen (though special plugs can be used to fill the holes.) Craig Sommerfeld, founder of The Kreg Tool Company, is credited with popularizing pocket screw joinery in the 1980s. The company today is the leader in creating the jigs, clamps and screws used to create pocket screw joints. Learn how to use a pocket screw jig in woodworking projects.