Hi,
Switches originally were assigned IP addresses for management purposes,like telnet into the switch and make config changes. Those were layer 2 switches such as 2950, 2900XL, 3500XL, 1900. Only 1 vlan interface or IP address could be used for management. Say for example you have 10 vlans on the layer 2 switch, you may assign all the vlans different IP addresses but then only one vlan interface would be up/up and pingable. The others wont be pingable although devices in other vlans work as desired.
Coming to layer 3 switches, you have as many vlan interfaces assigned IP addresses and all of them can be used for management purpose. Say for example if you have 10 vlans you assign 10 different IP addresses one for each vlan. these are more like logical routed interfaces which can be used for intervlan communication.
Here's a reference link:
http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a008015f17a.shtml
Best of luck for CCNA :)
