Taxonomy concept is something which confuses every new one there, even after "ahh got it now", confusions remain. For a sec, just think taxonomy is just the name given to the module, vocabulary is a definition which you have defined with some special properties and for certain content types (nodes), which further contains categories available for those content types. Terms are the "categories" under a vocabulary. While creating a content(node), you are able to choose terms and subterms and so on.
Node is basically a content type, which can behave as anything like page, blog entry, forum post or a custom created content type, like a job, project, etc. Node concept evolved as a need to have a content api which can be used to specify content of anytype, ever users or comments can behave as nodes using usernode or nodecomment modules.
Used drupal to build myspacematrix.com like 4-5 months back. And myspaceya.com being december's quick work. Myspace stuff sites don't interest anymore, though helped to start with, and also furnish the concepts
Also, always remember #drupal-support irc channel on freenode.net and Drupal Support forums at
http://drupal.org/forum