In Wikidata, an entity can be an Item or a Property.
An Item should represent a clearly identifiable concept or object, or an instance of a clearly identifiable concept or object. For example, in Wikidata we can have items for both the concept of planet (Q634) and an instance of a planet, Earth (Q2).
Items can and should also be linked to each other. Each item has a unique identifier (starting with a Q prefix) and its own page in the Wikidata main namespace.
A Property describe the data value of a statement and can be thought of as a category of data, for example "color" for the data value "blue". Properties, when paired with values, form a statement.
Both items and properties should contain at least a Label and a description in one or more languages.
You can find more informations aboutand on the Wikidata .