We only use a handful of common terms and conventions for the data made available over the API.
Unless otherwise stated anything called an Id (pageId, eventId, charityId) is the JustGiving Id, and is a 32-bit integer.
PageUrl, PageShortName and PageId; For a given Url of http://www.justgiving.com/my-page, the page Url is the entire string, the PageShortName is "my-page" and the PageId is the JustGiving Id for that page.
When supplying parameters to the API, you will be required to supply data in a combination of the Url called, the body of the request, and some optional query string parameters. By convention anything listed as part of the Url is required, the request body requirements will be outlined on a case by case basis, and any parameters listed but not appearing in either the Url example or the request body should be presumed optional. If you wish to supply these values they should be added as query string parameters.