An argument is a collection of one or more ideas organized into an outline. The first idea represents the writer's point, and the supporting ideas represent the reasons why the point is valid.
Arguments are what Goodpoint was designed to host. They are Goodpoint's "articles." A single idea is also an argument where the point is being made without any additional, supporting ideas.
A rule of thumb for ensuring that your point is an argument: your argument is something that a reader should be able to agree or disagree with.