Many authors confuse advertising with marketing. It's a common misconception, but advertising is only a small part of marketing.
Marketing can be described with the four P's. Product, Place, Promotion, and Price. Let's break each category down a bit.
To start with, your business that you are marketing, is yourself. You the author are the business. Your products are your books. So when we talk about marketing, we aren't marketing a single book or series. We are marketing you.
The place is the internet and any signings, books stores, or any place we can get you, the business out in the public eye.
Price is determined by market trends as well as what your business needs to make per unit sold to continue to run.
And finally promotions. Here is your advertising. Here is your public relations and your social media. Promotions get you and your products into the public eye.
A few amazing examples of Author marketing are John Grisham, Nora Roberts, or Steven King. Just hearing their names, even those that rarely read, have an idea of what the books feel will be. The name itself tells a potential customer that their product may be what they are looking for.
They have mastered the marketing game. With time, patience, and perseverance you could too.