When you save or export artwork, Illustrator writes the artwork data to a file. The structure of the data depends on the file format that you select.
There are five basic file formats—AI, PDF, EPS, FXG, and SVG—to which you can save artwork. These formats are called native formats because they can preserve all Illustrator data, including multiple artboards. (For PDF and SVG formats, you must select the Preserve Illustrator Editing Capabilities options to preserve all Illustrator data.) EPS and FXG can save individual artboards as separate files. SVG saves the active artboard only; however, the content from all artboards is displayed.
You can also export artwork in a variety of file formats for use outside of Illustrator. These formats are called non-native formats because Illustrator will not be able to retrieve all of the data if you reopen the file in Illustrator. For this reason, it is recommended that you save artwork in AI format until you are finished creating it, and then export the artwork to the desired format.