SEO, Search Engine Optimization (which is arguably the most effective at getting a good return on investment).
SEM (aka PPC), Search Engine Marketing via Pay Per Click.
SMO, Social Media Optimization (basically a form of Branding for the purposes of name recognition on social media).
VM, Viral Marketing - limited to unique, interesting, one time content.
Video Marketing (not to be confused with VM) - the goal is to make videos that useful to visitors to the website / youtube. They do not need to go viral or generate lots of views, the goal is to make useful videos that help clients, and in turn help generate sales.
VVM, Viral Video Marketing - the goal being to make one video go viral, which is unlikely because it is a numbers game and only a small percentage of attempts go viral. However VVM doesn't necessarily generate sales, because most people who end up watching the video are doing so because of amusement and have no interest in buying the product.
Branding, of which the primary purpose is name recognition, traffic is not the biggest concern - sales is.
Affiliate Marketing, requires people to take a commission on sales, which is often less than 0.5% of traffic or lower, depending on how good or shoddy a product is.
Note - I have (more or less) organized the above list in order of the most effective means of advertising down to the least effective means of advertising and building traffic. Some of the categories above may roughly tied in terms of effectiveness.