Why two different terms? There is a lot of stigma associated with self-publishing since a lot of authors eager to publish their own work often do so without any proper editing or feedback and the quality of the result is abysmal.
Another term you might want to familiarize yourself with is vanity press. Vanity press refers to companies that will take money to publish your book.
I hope this clarifies the topic and answers some of your questions, happy writing ^_^