The material is a non-woven polypropylene which does breathe and is durable. Here's the larger story:

Non-woven PP is made by taking polypropylene polymers and spinning them using heat and air into long fluffy threads, like cotton candy, then pressing the threads together between hot rollers to get a flexible but solid fabric with a weave-like texture similar to canvas. The texture leaves the fabric breathable, with a look and feel that is generally pleasant.

Is there a bottom or lining in the floor or is it open?