"Article" is a pretty broad term for any grouping of text that provides factual information, usually written in a style that is for general public consumption. The archetypal example is an article in a magazine or a newspaper.
"Tutorial" is a collection of information for pedagogical/teaching purposes. It is derived from "tutor", usually a one-on-one teacher. So it is writing, or video, or whatever media, that teaches in a manner similar to a tutor.
"How To" is kind of like a tutorial, but the word is slightly less formal. There is a tendency in unix/linux/computer science to use it as one word, often as a filename: HOWTO. For that reason, I tend to think of it as a more computer-science-y term, as opposed to "tutorial" which is more generic.
A "course" usually implies a series of lessons, most often in an institutional context (i.e., at a school or university).
A "track" is typically a set of courses, often held together by a certification or degree received at the end.