When you give your child a large gift, they pay CAT at 33% on the value above their threshold. If you pay that tax for them from your own money, the payment is a further gift, and it can be taxed again.
A Section 73 plan avoids that. It is a regular savings plan with an Irish life company, set up under section 73 of the Capital Acquisitions Tax Consolidation Act 2003. Money from it used to pay the tax on a gift you make within a year of the payout is exempt from CAT.