Self-publishing Is Not 'Vanity' Publishing
People sometimes refer to any self-publishing project in rather sneering terms as 'vanity' publishing. This is no cleverer than calling a shark a lampshade. They are two different things. As a freelance writer, I've come across this confusion many times.
Vanity Publishing: You've written a book and try for a publishing deal but get no takers. Feeling dismayed, you see an ad for a vanity publishing company (though they don't call themselves that) saying their professional editors will assess your work. You submit your manuscript and no matter what it's like — even if it resembles a child's homework put through a spin dryer — they say it has great merit. Next, they suggest getting some copies of your book printed to give to friends and family and, being very kind, they offer to take care of this for you. They arrange the printing at an extortionate fee about five times what it would cost you to just do it yourself. They profit and you end up with some copies of your book in the attic. It's all based on an appeal to vanity, hence the name.
Self-publishing: There's no vanity involved. You have a book worth sharing. You publish it yourself on a commercially viable basis for some or all of the reasons I've explained under 'Reasons To Self-publish'.