What is difference between hamd and shukur?

I was reading a tafseer of Al-Fatiha (in Turkish), and it is mentioned on that text that there are 2 kinds of ni'met (benediction), one is material and other is spiritual. It says that we shukur (thanks) to Allah for material ni'mets, and we hamd (thanks) to Allah for spiritual ni'mets. I thought both of them meant thanking. Can anyone explain what exactly hamd and shukur means and what is the difference between them?