Arceus is a Pokémon, and it holds a significant place in the Pokémon universe as it is considered the "God" or "Creator" of the Pokémon world. Here's some good information about Arceus:
Origin and Mythology: Arceus was first introduced in Generation IV of the Pokémon games (Diamond, Pearl, and Platinum) and is known as the "Original One" or the "God Pokémon." According to the in-game lore, Arceus hatched from an Egg in a place where there was nothing, and it shaped the universe with its 1,000 arms.
Typing and Ability: Arceus is a Normal-type Pokémon. However, it has a unique ability called "Multitype," which allows it to change its type depending on the Plate or Z-Crystal it holds. With this ability, it can become any type, making it incredibly versatile and powerful.
Plates: Arceus's ability to change types is based on the Plates it holds. There are 17 different Plates, each representing a different type. When Arceus holds a particular Plate, it becomes that corresponding type, granting access to moves of that type and boosting the power of STAB (Same Type Attack Bonus) moves.