Dependency resolution in npm -- How npm downloads node modules

When you download a module from npm server then how npm reads the dependency tree and how it download the dependent modules of a module.
What happens if different module depends on same version of a particular module of different version of a particular module.

[akshayrajput]

Hello thanks for the detailed explanation is it possible to have non flat dependency for a specific package in npm version 6, I.e even if package b is of similar version in A and C I want both of them to download seperate package internally

[appleproductipodtouch]

keep up the good work.
was not expecting to find a video about this topic
Glad that you did.
small suggestion, you could work on the way you explain.