What is the difference between an untagged port and a tagged port?

[MUNIR_ENG]

What is the difference between an untagged port and a tagged port ? when can I using them & what is the benefit?

[Bruce_Garlock]

I think you also need to 'untag' the native vlan (not default vlan) on any trunk ports.

[Erik_Auerswald]

Using a "native VLAN" on a trunk means not tagging this VLAN. This is not needed for Extreme EOS nor ExtremeXOS. I would recommend to tag every VLAN on any inter-switch-link. Note that some special configurations (e.g. RSTP on EXOS) do require a native VLAN, but those situations can usually be avoided (e.g. using MSTP instead of RSTP).

[Ryan_Mathews]

This is a pretty solid explanation as well:
https://gtacknowledge.extremenetworks.com/articles/How_To/Understanding-EXOS-VLANS-and-tagged-and-un...

[davidj_cogliane]

End user devices will need to be on an untagged vlan to get to the internet.

[MUNIR_ENG]

great , just i need know What is the function untagged, with what use, witch the benefit ?