Google Visualization API gadgets are gadgets that can access data sources in an easy manner. For developers this means writing an application only once to be reused over multiple data sources. For users, this means enjoying a wealth of new visualization options over many types of data sources.
Curently Google Spreadsheets supports visualization gadgets.
Visualization gadgets read data from a data source, and display this data in a useful way. The data source is typically configured in a gadget as a URL in a gadget preference called data source URL.
Visualization gadgets will prompt you to fill in a data source URL. Data source URLs are provided by applications that support the Google Visualization API. For example, to get the data source URL from a Google Spreadsheet, do the following: