Identifier
IdIdsNamespace idNamespace idsNamespaced stringNamespaced stringsResource idResource ids
Identifiers are a way to declare and identify elements in Minecraft like items, block and entities.
Identifier can be made with lowercase letters (abc…), numbers (123…), underscore (_), hyphens (-) and dots (.).
Identifiers follow this structure namespace:name, where the namespace is the name of the folder from the Datapack or Mod where the item is located, and the name is the name of the .json file where the resource is declared.
For example, if I want to obtain a glass block using Commands I would type:
/give @s minecraft:glassminecraft:glass is the identifier of the glass block and minecraft is, of course, the namespace of Vanilla items.