Where can an explanation in layman's terms of 'relevant representation' be found and where in the Act is it defined ?

The glossary on the IPC's web-site provides a plain English explanation (see
attachment 1)
The 2008 Planning Act (PA 2008) states at s102 (4): "A representation is a relevant representation for the purposes of subsection (1) to the extent that?
(a)it is a representation about the application,
(b)it is made to the Commission in the prescribed form and manner,
(c)it is received by the Commission no later than the deadline that applies under section 56 to the person making it,
(d)it contains material of a prescribed description, and
(e)it does not contain?
(i)material about compensation for compulsory acquisition of land or of an interest in or right over land,
(ii)material about the merits of policy set out in a national policy statement, or
(iii)material that is vexatious or frivolous"
The Interested Parties Regulations, Reg 4 further defines a relevant representation.
S56 (4) PA 2008 states: The applicant must, when giving notice to a person under subsection (2), notify the person of the deadline for receipt by the Commission of representations giving notice of the person's interest in, or objection to, the application.