What are the materials used for scaffolding?

In Europe and the Americas, scaffolds are typically constructed of steel tubing, which gives good stiffness at low cost. Some frame elements are welded together but other clip together so that the scaffold can be disassembled for shipment or storage. Planks for workmen to stand on are typically plywood.

Bamboo is still used for scaffolding in South Asia. I have seen high quality steel scaffolding on large buildings in China.

For small projects in the West, many builders will temporarily nail together 2x4" lumber to make a scaffold. The nails (or screws) can be removed so that the wood can be moved to another location and reused.