With this briefing we provide relevant definitions for file types, formats, data bases and concepts commonly used in climate and energy system modelling. We offer this document, because not all data is created equal. We have to deal with a multitude of data sources for input and output. Some information comes in special formats and some information can be stored in different ways. Each way comes with specific advantages and drawbacks. Sometimes, conversion is needed and may not be straight forward. These particularities are important with respect to reproducibility, comparability, re-use and documentation. We lay out a reference to allow a productive approach in working with commonly used file formats and related issues in climate and energy system modelling. We introduce binary and text based file formats, the difference between vector and raster formats, the classification of the structuredness in data, and the use of databases. Subsequently, we provide a description of specific commonly used formats from all categories. Whenever possible we reference an external resource for further explanation. Finally, we conclude with a short section of best practices and recommendations. This briefing may develop further and is open to suggested additions by anyone. Please post suggestions here on github. Please attach the label formats-briefing to your issue.

This work was supported by grant 03ET4057A--D (SzenarienDB) from the Federal Ministry for Economic Affairs and Energy of Germany (BMWi).