I usually refer to them as "texts."

An article and an essay are pretty interchangeable, they're both short writings (more than a paragraph, but not an entire book) on a subject. Article tends to be used more for publications (magazines, blogs, etc.). Essay tends to be used more for things you have to write as part of schoolwork. A journal has different meanings. Either it's a publication (usually a magazine or newspaper) on a particular topic or field, or it's a regular (often daily) writing such as a diary. So, if you're writing something in a notebook and not publishing it: Article could fit, but we'd probably not call it that without publishing it. Essay would fit if it's about a particular thing. Journal would be a great fit if it's something like a diary entry, but a bad fit otherwise. Note would be a good fit if it's something really short (maybe not even a full piece of writing), mostly to be used as a memory aid, study aid, or record.

Thanks @Duncan.

They could be any of the three. - An article is normally some form of journalistic writing, whether in a newspaper a blog, etc. - An essay is a structured piece of writing, some sort of assignment. It should include an introduction, discussion and a conclusion. You might hear essay used as a word for a really long piece of writing: "when you said you would send me an email, I didn't think you were going to write an essay!" - A journal is a sort of diary entry where you notate things you did or thoughts and ambisions, etc.