How to start with API?

[bettinz]

Hello,
I'm starting an application that load products from an external source, and then it sync everything with virtue mart.
I use VM every day, and I know the table system. So, I can execute query for products, categories, prices, etc; but what I want is to use VM's API.
VM API is not dependent by VM version, and it's more clean. I've looked at the documentation, but it's not really helpful.
Have anyone used VM's API and can help me to start the work?

Thank you everyone.

[Milbo]

Lets say it is the goal that the api does not change, you already use the API.
This gives a start http://dev.virtuemart.net/projects/virtuemart/wiki/Developing_a_module_or_plugin_for_VirtueMart_2