Data description
Depending on the database you're using, you'll have more or less detail on its calculation.
If you're using FD E01-008, the database is not very well documented, but you can find information in the document of the same name (it's a documentation booklet).
If you are using Base Impact, you can create your own access on https://base-empreinte.ademe.fr/ to access the data.
If your license also includes (fee-based) access to ecoinvent, you can access the full documentation at https://v38.ecoquery.ecoinvent.org/ (level of detail depends on your ecoinvent license).