Explanation/Reference:
VLAN Trunking Protocol (VTP)
Reference:
http://archive.networknewz.com/2004/0317.html
Explanation:
VTP Modes
Server Mode Once VTP is configured on a Cisco switch, the default mode used is Server Mode. In any

given VTP management domain, at least one switch must be in Server Mode. When in Server Mode, a switch can be used to add, delete, and modify VLANs, and this information will be passed to all other switches in the VTP management domain.
Client Mode When a switch is configured to use VTP Client Mode, it is simply the recipient of any

VLANs added, deleted, or modified by a switch in Server Mode within the same management domain.
A switch in VTP client mode cannot make any changes to VLAN information.
Transparent Mode A switch in VTP Transparent Mode will pass VTP updates received by switches in

Server Mode to other switches in the VTP management domain, but will not actually process the contents of these messages. When individual VLANs are added, deleted, or modified on a switch running in transparent mode, the changes are local to that particular switch only, and are not passed to other switches in the VTP management domain.