Like all Mainstream Pokemon Games, Pokemon Sword & Shield introduces brand new items to the World of Pokemon. Most of these items are either Nature Mints (which can be used to change the nature of a Pokemon), EXP Candy (which can be used to increase the experience of a Pokemon), Dynamax Crystals (which can be obtain via Wi-Fi Events to cause certain Pokemon to Dynamax at Watchtower Liar), or various food items that can be used to make Curry in your Pokemon Camp.
Additionally, there are a number of new items that will help players evolve certain New Pokemon (Sweet Apple, Tart Apples, Sweet Items, Pot Items), as well as handful of new Competitive Battle Items (Throat Spray, Eject Pack, Rusted Sword, Rusted Shield) and Fossils (Drake, Dino, Bird, Fish). Of course, there will also be various Key Items that players will obtain throughout their journey, some more useful (Rotom Bike) than others (Sonia's Book).
We have questions and answers related to this topic which may also help you: