Record chart are a method of ranking music according to popularity during a given period of time. Examples of music charts are the Hit parade, Hot 100 or Top 40. They are primarily a marketing or supermarketing tool like any other sales statistic, they have become a form of popular media culture in their own right.
There are lots of different criteria used in different charts used to reflect popularity, commonly: sales of records, cassettes and compact discs; amount of radio airplay; and recently number of downloads.
Some charts are specific to a particular musical genre and most to a particular geographical location (although download charts are not easily pinned down in this way). The most common period of time covered by a chart is one week with the chart being printed or broadcast at the end of this time. Summary charts for years and decades are then calculated from their component weekly charts. Component charts have become an increasingly important way to measure the commercial success of individual songs.
A Chart Hit is an extremely popular recording, identified by its inclusion in a ranked list - a chart - of top selling or otherwise judged most popular releases. Chart-topper and related terms like No. 1 hit, top of the charts, chart hit, and so forth, are widely used in common conversation and in marketing, and loosely defined. In North America, the weekly charts from trade publication Billboard magazine are most often referenced (quite often internationally, as well), particularly the Billboard Hot 100 singles and Billboard 200 album charts, although there are many other charts and sources. Because of its value in promoting artists and releases, both directly to the consumer, and by encouraging exposure on radio, TV and through other media, chart positioning has long been a subject of scrutiny and controversy. Chart compilation methodology and data sources vary, ranging from buzz charts based on opinions of various experts and tastemakers, to charts that reflect empirical data, like retail sales. Therefore, a chart-topper may be anything from an insiders' pick to a runaway seller. The term is also used similarly to some extent in video games.