Promotion, Advertising or Sharing information
The differences between Promotion, Advertising, Sharing information and Profile raising may perhaps be more of intention than method since they share many common traits.
With Marketing as in most of life, Communication is often the most important part of sharing information with a target audience be they friends, colleagues or others.
Promoting goods and services has always been a challenge, with word of mouth being the oldest, cheapest, most effective, immediate and fortunately in the internet/smartphone world easily replicated with Google's +1's, Facebook likes, Twitter tweets, LinkedIn recomendations, personal blogs, etc. Real world advertising spaces such as billboards, magazines, noticeboards and shop windows complement and also have their equivalents in cyberspace. The challenge of getting and keeping someone's attention is the same only more so. Get it wrong and it may be hard to recover from the fallout, get it right and it can appear effortless and magical; fortunately with testing it's easier to avoid the former and the latter can be easier than you think.
Communication is often the most important part of sharing information with a target audience.
The most important thing about communication is that it is done. Getting the message right, consistent with other messages and appropriate is more about effectiveness and thus a better return on investment.
As the Communications part of Marketing Communications, in the Marketing Mix it is the Promotion part of the 4Ps, Communication in the 4Cs and Information in SIVA.