what happens when we apply different base line patch?

what happens when we apply different base line patch in oracle applications?


The patch  will failed with the below error.
============================
AutoPatch error:
--------
This patch is not compatible with your current codelines.



Current target release is 12.1.3

AutoPatch error:
--------
This patch is not compatible with your current codelines.

This patch is compatible with: entity 'ar' - codeline 'R12.AR.A'.
Your current on-site codeline for the entity 'ar' is: 'R12.AR.B'.

You should not apply this patch.

Apply an equivalent patch that is compatible with your
current codelines instead.
--------


AutoPatch error:
--------
A fatal error related to codelines or codelevels has occurred.

See messages above for details.
--------
You should check the file
/u01/erpapp/appl/admin/erptest/log/11808198.log

for errors.

[apptest@ctsst 11808198]$