Wikimedia/How Wikidata works
Wikidata is a very complex website, and will require a page in this book to explain. Wikidata primarily consists of two things: items and properties. Items are prefixed with a Q, whereas properties are prefixed with a P. There are other pages on the wiki of course, but these are the basics. An item in itself is very complex, and may appear disorientating to a new member of the community.
Once a new item is created, it will be created with a Q prefix, and a number. This is basically the what number item it is, for example: Q10 is the tenth item, Q123 is the one-hundred-and-twenty-third item and so on and so forth. There are around 10,000,000 items available on Wikidata. The first part of an item is the label, basically the title of the item. There is one label for every language, not one for all languages.
Second is the description, describing the item. There is again one description per language. The third part is the list of aliases. There can be an unlimited amount of aliases per language, unlike labels and descriptions. The fourth part is the properties, where properties are defined. This can be date of birth, date of death, occupation, given name etc. There are many properties that can be defined, but not all properties apply to all items.
The fifth, and arguably the most important part of an item is the interwiki links. These link Wikipedia, Wikiquote, Wikivoyage and Wikisource pages to an item. Once a page is linked, a full list of different languages will appear down the sidebar of the desired article, allowing quick navigation between languages.
Properties are a lot less complex. They require a special right to create, this right can only be granted by administrators. Properties only consist of three parts, a label, a description, and a list of alternate aliases. That's all there is to it. Once created, these properties can be easily defined in any item. All properties defined can be referenced, but these do not have to be via URLs. The user can state that it has been imported from a Wikipedia, i.e. the English Wikipedia, Spanish Wikipedia, Dutch Wikipedia etc.