What are the channels for attracting customers to an online product?

Question

Marketing

Hello.
I want to understand the following question a little.
What are the ways to attract an audience to an online service or product?
Not tied to a country.
Now I know that it is important to promote or buy contextual advertising, articles in social networks. But I don't think I know much anyway.
Of course, in each case there are different channels for influx of customers, but I need exactly a list of all possible ways in order to study each one and roughly understand which ones are suitable for certain online products and which ones are not.
Thank you.