Mapbox Studio Classic has two different editors: style and source.
The source editor in Mapbox Studio Classic allows you to add one or more vector or raster files and turn them into vector tilesets or raster tilesets, respectively. You can then upload these tilesets to your Mapbox account for use in Mapbox Studio or our other APIs. Your uploaded source will appear up on your Data page with a map ID so you can use your data with other Mapbox tools.
Check out the Mapbox Studio Classic source quickstart to learn more about working with data in Mapbox Studio Classic.
The style editor allows you to write CartoCSS to style the map. This can be anything from changing the font labels to the color of the streets. From Mapbox Studio Classic’s style editor, you can also add your data from the Layers panel by referencing its map ID. Next, you can write CartoCSS to style your data. Your uploaded style will appear on your Classic styles page with a map ID so you can use your style with other Mapbox tools.
Check out the Mapbox Studio Classic style quickstart guide to learn more about styling in Mapbox Studio Classic.