[DOC]: provide more explanations

[iulusoy]

Location of the documentation

https://github.com/ssciwr/biocypher/tree/restructure-docs/docs/learn/explanation

Documentation problem

The explanations section is incomplete and not harmonized

Suggested fix for documentation

Provide more content and harmonize with OntoWeaver material

Code of Conduct

• I agree to follow this project's Code of Conduct