im new to virto Commerce i just downloaded it and ran it , so how can i understand how the functionality of the virto works, like for example the "cart" how dose it get filled up and how the platform knows about it ? most likely apis but can any one show me how it works in details or maybe a documentation for tutorial or something ?
VirtoCommerce has official site and good docs. It has no special workflow that describes how it works, but it has some diagrams & docs (even at main page) that describe platform in common words. Also, there is many topics in docs, that describe specific cases, like module development & installation. You can start with this tutorial.