well ecc memory has a ninth chip (ecc chip) on the memory module, whereas normally it would have eight ... so that is how your going to find out if you are using ecc memory ...
the module is also identifed as a 71 or 72 bit dimm instead of a 64 bit dimm, and ecc uses these extra 7 to 8 bits to verify the integrity of every 64 bits stored on the module and correct any error when possible ... and although it costs more, it is more reliable ..
but your first step would be to see if your board supports ecc memory, rather then contemplating on whether to buy it or not ... this info can be found by either :
a) looking in the cmos setup for a feature to enable/disable it
or
b) looking in your motherboard documentation booklet ...
so in conclusion the difference is basically the error checking like described above, not so much a performance increase, so hopefully i answered both of your questions
