Comparison of geodata formats

ESRI proprietary formats

Coverage - ancient, dead format still widely in use by people clinging to the last remaining copies of ArcInfo. ESRI no longer provides any reasonable documentation. Good luck. See this Library of Congress doc: https://www.loc.gov/preservation/digital/formats/fdd/fdd000284.shtml

Personal Geodatabase - deprecated, based on obsolete 32-bit Microsoft technology

You can add an entire Feature Dataset to a ArcMap with drag-and-drop from ArcCatalog. I find this handy.

File Geodatabase - File based, still highly proprietary but accessible via an API that is free.

Layer file - When you save a layer file, the file filename.lyr is created for the layer to store symbology design and layout information, so that you can reuse those settings in other maps.

Open formats

Shapefile - Pretty much "owned" by ESRI but everyone has adopted it. A "shapefile" is really a collection of files with the same name but different extensions.

The projection (if it is defined) is stored in filename.prj. This is an ASCII file. You can cheat and copy and rename it to define projection on other shapefiles; of course, this does not reproject data. Shapefiles created with ArcView 3.x do not have prj files.

Tabular data for attributes is stored in a DB IV format file called filename.dbf

When ArcCatalog creates metadata for the file, it puts it in filename.xml.

Data interchange formats

ESRI ASCII (e00) format