connecting to a wireless router with another vendor wireless nic?

hi
I had a problem using a DLink DWL-G650 to a Linksys wireless router the
other day - I've since returned the card (it was dual b/g but never could I
surf reliably.. I'd get an IP but not be able to connect.) and paid a nice
restocking fee but the clerk asked me if I had changed the SSID? so that I
could connect to the linksys router - I've no idea what ssid is but I do
know that the non-g version of this card was working just fine on the same
router.

Does anyone know what SSID is? or how to get to it so that in the future I
can change mine if I have the same problems.

thanks, rgooding77