This contains:

16 Scarlet & Violet—151 booster packs
1 metal card with hyper rare Mew ex
1 special, rare promo card with Mew ex
1 rare promo card with an illustration of Mewtwo
1 play mat with stitched edges with Mew
1 deck box
1 coin with Mew
Various gameplay accessories
The full set of Scarlet & Violet 151 will include:

More than 160 cards
12 Pokémon Ex
All 151 Pokémon originally discovered in the Kanto region, in Pokédex order
More than 10 Trainer cards
16 illustration rare and seven special illustration rare Pokémon and Supporter cards
16 ultra rare full art etched Pokémon and Supporter cards
Three hyper rare gold etched cards