This is a "baby" version of the standard Australian proof coin set for the year. It contains all the regular circulating denominations except the 50 cents; instead of the "definitive" Coat of Arms type, it has a special Possum Magic non-circulating 50 cent collector coin with a coloured reverse.
The Royal Australian Mint says about this year's set:
"Relive the magical adventures of possums Hush and Grandma Poss with this beautiful baby set of proof coins, celebrating the beloved Australian children’s book Possum Magic by Mem Fox and Julie Vivas. With a special colour printed 50 cent coin reflecting the gorgeous illustrations of the book, this special set makes a traditional and uplifting gift to welcome a new little possum into the family."