Realtek AC'97 audio is usually (if not always) on-board sound,
which means that it's a sound chip integrated into your
motherboard, rather than being a separate removeable sound card.
They are very common but come in lots of different
implementations.
The simplest way to find out is to refer to your motherboard
manual or the documentation that came with your
PC. If it refers to front and rear speakers, then
it at least support 4.0 sound. If it refers to "6 channel" sound,
then that usually means 5.1 surround sound.
Alternatively, if you have a sound card utility or
application installed for that sound chip (e.g. SoundMAX),
then there's often a configuration screen to switch between
different modes