Hi, new member here, so maybe in the wrong part of the forum?

I often come across IPRG in airline rules. What thas that mean?

Thanks,

Example:
CATEGORY 5 ADVANCE RESERVATION AND TICKETING UNLESS OTHERWISE SPECIFIED NOTE - RULE WEEK IN IPRG100 APPLIES

CATEGORY 6 MINIMUM STAY UNLESS OTHERWISE SPECIFIED NOTE - RULE EU02 IN IPRG APPLIES