Here is a short list of common terms with my version of their definitions and in their hierarchical structure.
Online (or Web Site) Marketing: I think a case can be made that online marketing and website marketing are two different functions, but only slightly. However with the advent of pay-per-call it will be entirely possible to market your online without even having a website. Not sure if that would be advantageous or not, but possible. I place a distinction here between online marketing and search engine marketing because the functions of online marketing , while including search engine marketing, may bypass the search engines altogether.
Examples: email marketing, link buying, renting or exchanging (when done for exposure, not search engine relevance), online ad placement, website design, usability, conversions, etc.