Online Marketing is the big overall umbrella term for all types of online marketing efforts:
Search Engine Marketing
Referrers and Links
E-Mail & Newsletters
Banner Advertising
At the heart of the internet are links from one website to another. Links allow people to move from one website to another - and is one of the most important ways that people flow on the web. Of course, getting lots of webmasters to link to you is important but it's also difficult. If you are lucky to be very well known and connected, you may get many links automatically. If you are, then you might get a lot of visitors from this - if not you will want to consider how to increase this or approach a Search Engine Optimiser to help you identify and improve your inbound links.