Yes. Everything degrades (or decomposes) over time, but some things take longer than others. This depends on the base material and the conditions in which the thing is decaying in (temperature, humidity, air and time). A general rule of thumb is that if something is a natural product it breaks down naturally (mother nature at work), whereas a man-made product can take forever to decompose (think about concrete when you think about petroleum-based plastics). Natural degradation is a better option.
Biodegradation means that the molecules (that form the material) are created and bound in such a way that natural “living” micro-organisms (bacteria, fungi and algae) will consume and breakdown the molecules. This releases the bonding of the molecules and thereby speed up the degradation. There are chemical and physical degradation processes taking place, both accelerated due to the involvement of living organisms (hence the term biodegradation).