PROMOTION:
 
It is an activity that will help you to sell your products or let others know your company better.
  • A message issued on behalf of some product, cause, idea, person or company.
  • An act of raising in rank or position.
  •  Encouragement in the progress or growth or acceptance.
  •  The advancement of some enterprise.
Context examples: 
  • Advertisement: a public promotion of some product or service, a promotional statement.
  • Communicative processes – highlighting the message from the giver to the recipient
  • Promotional materials, Publicity, Packaging of new idea/items, promotion that supplements or coordinates advertising
  • PR: a promotion intended to create goodwill for a person or institution

Marketing: the commercial processes involved in promoting and selling and distributing a product or service


And self promotion?
 
Self-promotion means exactly what it sounds like:
 
  • To promote yourself/company in order to get publicity and to be well sought after.
  • somebody runs for office they send out campaigns in order to get the people to vote for them in the election.
  • If a person went on a talk show to talk about achievements and plans for the future.
  • These are all "Self-promotion"

Using promotional materials and branded items has the potential to reach a far wider audience, create goodwill and be remembered.