Tagged vlans - generally used for ports that are connected to other switches = cisco trunk
Untagged vlans - = cisco access
Tagged vlan = we tagged more than one vlan in the trunk port?
Untagged vlan = we just configured the switchport as access port?
**Tagged: Allows the port to join multiple VLANs
**Untagged: Allows VLAN connection to a device that is configured for an untagged VLAN instead of a tagged VLAN. A port can be an untagged member of only one port-based VLAN. A port can also be an untagged member of only one protocol-based VLAN for any given protocol type. For example, if the switch is configured with the default VLAN plus three protocol-based VLANs that include IPX, then port 1 can be an untagged member of the default VLAN and one of the protocol-based VLANS.
REMEMBER! Uplink between switches must be both tagged on same VLANs.
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i hope this gives you an idea of tagged and untagged :)