docs: improve datasource (#7734)

Co-authored-by: Rhys Arkins <rhys@arkins.net>

docs/usage/modules/datasource.md

 # Datasources
 
-Once Renovate's Managers are done scanning files and extracting dependencies, they will assign a `datasource` to each so that Renovate then knows how to search for new versions.
-You do not need to ever configure/override Datasources directly, but you may use them in `packageRules` to configure other aspects of Renovate's behavior, e.g.
+Once Renovate's manager is done scanning files and extracting dependencies, it will assign a `datasource` to each extracted package file and/or dependency so that Renovate then knows how to search for new versions.
+You do not need to ever configure/override datasources directly, but you may use them in a `packageRules` array to configure other aspects of Renovate's behavior, e.g.
 
 ```json
 {