Hi,
It refers to OSI layers.
Here is a tut on that subject :
http://www.foo.be/cours/cisco/html/node3.htmlSo be simple, layer 2 refers to MAC addresses, you can manage that, which is a switch basis.
Layer 3 is network layer, that is to say, between others, IP addresses.
When a switch is layer 3 manageable, it means that you can do more things than on layer 2, for example create VLAN, access list (allowing or refusing some addresses), with the only need to know the subnet, and not necessarily each MAC address...
ON layer 2 management, you can handle only MAC, wihci means that usually you can't manage pretty much this kind of swicth, apart from entering each MAC address...
Tks to assign points if useful ... don't hesitate to ask for more details on specific product comparison if required.
hth
J