How many different DVD-ROM region restrictions are there?

The setting on DVD Drive (with 2 types):

• Phase I (no region restricted) – This type of DVD-ROM depends on the software to control the region. If you put in a DVD title of a different region, PowerDVD SE will allow you to change the region code, on this type of DVD-ROM. You will be limited to 5 region changes however.
• Phase II (with region restriction) – The region is restricted by the DVD-ROM. Please contact your hardware company (DVD-ROM company) about this issue, since this is hardware restriction, PowerDVD SE will follow the hardware restriction.