What dose the address mean in CCS5?

The address is the PC that was pushed onto the call stack at that point. In this case it is showing the start of your memory space. Here it is only showing the address as there are no symbols loaded for that location. For the other entries in the stack it is showing you the symbol info. For example address 0xC0051504 maps to the OS_TaskIdle function at line 1739 of os_core.c