views Relationships and argument? What are the relationships and arguments in Views? How do I use them? I have read some tutorials, but still don't know how to use them. Can someone explain them more clearly? Thank you.
Relationships are the way Views expresses SQL joins. For example, when viewing a node, you can add a relationship to it's author, pulling in even more data.

Arguments have been renamed "Contextual Filters" in Views 7.x-3.x, which is a better name. Basically, it's a filter that gets its input from the the page, either by the page's URL or the node or user being viewed, etc.