Shipping and moving boxes are made of a paper material called "corrugated" or "corrugated paper". A cross section of some corrugated is shown.
This picture represents a material called "single wall corrugated". The vast majority of all boxes are made of single wall corrugated.
This picture shows a material called "doublewall corrugated" which is usually much stronger than the "singlewall" material described above.
Strength of single wall corrugated (or double wall) varies a lot depending on the materials used in construction. There also exists "triplewall corrugated". This material is frequently designed to meet military specs. It is usually treated for extreme strength and moisture resistance. This makes it incredibly strong and incredibly expensive. If you feel you need triple wall strength, it might be easier to purchase crates, instead.
Flutes is a sheet of corrugating medium that is shaped into a continuous rolling wave. Observed vertically, they form a row of columns, basically a structure form capable of supporting great weight. Viewed horizontally, the flutes are arches. Flutes serve as protective cushioning and helps strengthen a carton
