An inscription TX is a non monetary TX abusing the bitcoin monetary network as a blob data storage with the inscriptions exploit, which abuses the lack of limit on the tapscript size.

We had a script size limit with SegWit v0, which was limiting the script size, by filtering bigger scripts. This limit doesn't exists on Taproot tapscripts.

Here is an old PR from Luke:

https://github.com/bitcoin/bitcoin/pull/29769

Lack of this filter created a parasite protocol on top of Bitcoin monetary network called Ordinals or Inscriptions abusing the network.

An example TX exploiting the network:

https://mempool.guide/tx/3f168c5a46a8b99797c510037b2c12a5ef97d0aaa463b09a5be972b7c6416a54

If you press "Details", you will see that this TX is spending an V1_P2TR output, and inside the tapscript (which is decoded version of witness as tapscript) there is:

OP_0 // false

OP_IF

[data]

OP_ENDIF

As you can see, this is easy to stop. You can either filter anytime something like Inscription shows up and you can detect and filter them. Or you can just put a limit on the tapscript size. Both methods work, and doesnt create any issues what so ever for the bitcoin users.