There are a few things that I read about for various computer components that I just don't understand and I was hoping someone could give me an answer. For hdds, what is the buffer? And what is the average? Also, sometimes listed as a feature is something like fluid dynamic bearing spindle motor technology. What is that?
And regarding RAM - What are the different speeds? What is the significance of ECC? What is buffering, cas latency, bandwidth, and organization?

ok,
the buffer is a small ammount of memory inside the HDD that data is stored too (typically 2mb but can be 8 on some good ones)
The reason a hdd needs this extra temporary storage is because every so often the read/write heads on the disk platter need to re-align/reconfigure themselfs and during this time nothing can be written/read so the data to be written is instead stored to the buffer to reduce waiting times and write errors.
by average i assume you mean average seek time, this is the time the read heads on the HDD take to find a random peice of data on the drive (not realy revelevent in the real world but the if your brand gets a lower number than your compettitors then you show it off! )
the fluid dynamic spindle motor is the type of motor used to spin the hdd round, they use lube and ball bearings to keep the drive quiet when it is spinning and also to reduce friction and therefor heat (wich relates to the buffer as the heat from the motor reduces the air density and makes the read heads re-configure themselfs...)
the different speeds in RAM are the same as the different speeds in a processor, exept a bit lower ( ~ 166Mhz - 500Mhz these days) the higher the frequency the faster the signal goes through the memory
ECC - no idea!!
buffering in memory - no idea, similar to Hdd buffers but used as to que memory things....?
cas latency is the time it takes a command to get from one part of the memory to annother (not sure where, i'v read it somewhere though) the lower the number the better i have the option of 2, 2.5 and 3 in my bios, but to be honest you wont see the difference in anything other than benchmarking.
bandwidth is the ammount of data that a component can handle at any one time, be it 6gb a second or 10mega-bits per second
organisation? no idea!
hope it helps....