Link to CPU-Z: http://www.cpuid.com/cpuz.php
The green box tells us the general type of memory and the total size of the memory. In this case, the system contains 512 MB of DDR2 memory.
The blue box tells us if the system is running in single or dual or triple channel mode. In this case, the system is running in single channel mode.
The red box tells us the frequency (speed) of the memory (CPU-Z will give you the actual clock speed, not the DDR equivelent), the FSB (Front Side Bus) to DRAM ratio, and the actual memory timings that are currently set within the BIOS. In this case, we have 533 Mhz (266MHz x 2) memory running at 4-4-4-12 timings.
The SPD tab is just showing the timings that are pre-programmed into the SPD chip. They DO NOT indicate what the memory is actually running at.