What exactly is polished concrete?

"The act of changing a concrete floor surface, with or without aggregate exposure, until the desired level of finished gloss is achieved by using one of the listed classifications;  Bonded Abrasive Polished Concrete, Burnished Polished Concrete, or Hybrid Polished Concrete." -Concrete Polishing Association of America

What is urethane cement and why do I want it in my...
Is your concrete too wet?