I am thoroughly confused about this. I need to know exactly what it is so I install the right applications and have better understanding on why some may not be working very well. I have an HD2. I don't know if it is OFFICIALLY a pocket pc or a smartphone. its running WinMo 6.5. According to Wiki its a smartphone, but sometimes when I try to install an app it says "this app is not a valid pocket pc application". Ugh.. Any help would be appreciated. Thank you!

It is a "pocket pc". It is synonymous with the "smartphone" these days. Of course, there is a windows mobile smartphone OS, but that is a different story.

However, keep in mind that apps you install on the device need to be in .cab format, unless you installing through a PC. You might be trying to install .exe files that cannot be installed on a pocket pc., and need to go through the activesync (connect your phone to the computer with a cable or pair it through bluetooth).