Marketing is promoting a service like an exchange.
It can be even more than that.  It can be about selling a brand, or even a lifestyle.
Yes I agree.  Self publishing of a book is a type of marketing.
You're quite right, especially if part of selling the book you're trying to get a message through, or starting to get the word out of you as an author.
Some of the best author solutions are Palibrio and Booktango.
I've never heard of those before.  Are those publishing houses, or services kind of like how an author can have their books published via Kindle?
They are parent companies.