DEMs are files that contain either points (vector) or pixels (raster), with each point or pixel having an elevation value. They come in a variety of file formats, from .csv to .dem to .txt, and you can derive lots of other information - like contours or 3D surface models - from them.
There are a few terms that may be encountered that have subtle but key differences:
- DEMs: digital elevation models represent the land or "bare earth" (no trees, buildings, etc.)
- DSMs: digital surface models represent the reflective surface of the earth (bare earth plus trees, buildings)
- DTMs: digital terrain models are either synonymous with DEMs or comprised of a network of vector points instead of a continuous raster
- Further details here and here
Is the file format you have not listed here? Contact us and/or consult lists of all raster and DEM file formats supported by ArcGIS Desktop, ArcGIS Pro, Global Mapper, and QGIS.
This information is accurate for ArcMap Desktop 10.8, ArcGIS Pro 3.0, Global Mapper 22, and QGIS 3.16.