Cardboard is term used for paper board used for packaging. This can be made of single sheet to multiple sheets of paper or other combination like multiple corrugated layers. They are glued to gather to impart strength in particular direction. Over the years the material has been improved by use of water proof material etc. Now a days , polythene sheets are also fused to top layer to impart tear strength. Natural or synthetic fabrics/metal sheets are also sandwiched for better strength and to meet specific requirement.