Hello Karan
Frames that are sent from almost all network devices such as computers, are sent without tags. Frames sent out of access ports on switches are also sent without tags. Tags are only added when a frame exits a trunk port and are removed once again when it enters the trunk port on the other end. Tagged frames should only exist on the link between two switches connected via a trunk.
Having said that, the Native VLAN is set up on a trunk so that any frames that do arrive on that trunk port without a tag will be placed on the appropriate VLAN. Situations where this is used is when switches communicate with each other using control frames such as those use in the CDP, VTP and STP protocols.
Another situation in which the native VLAN can be used is depicted in this topology:
Now the network shown above contains a very bad network design and should never be replicated, but it is used to prove a point. PC1 is connected to a hub which is in turn connected to Switches A and B. The link between Switches A and B (via the hub) is a trunk connection. Any frames sent by PC1 will be sent without tags, so untagged frames will reach the trunk ports of Switches A and B, due to the hub. Those frames will be placed on the configured native VLAN on each of those trunk ports.
An untagged frame is not a frame with an error, it is just one that doesn’t include the tag. This would not show up as an error so it wouldn’t be caught by the checksum mechanism.
I hope this has been helpful!
Laz