par ailleurs

Meaning

Adds an element of a DIFFERENT kind: you change angle without leaving the topic.

Position and punctuation

at the start of the sentence · a comma after

Example

Le budget a été voté. Par ailleurs, un comité de suivi sera désigné en janvier.

The budget has been passed. In addition, a monitoring committee will be appointed in January.

In the DELF

the B2 essay · the C1 synthesis

The trap

PAR ailleurs adds a NEW point; D'ailleurs reinforces the one just made. They are not interchangeable, and that is the most frequent confusion at B2.