Hi Steve
Firstly why backlink. The simple answer is it gets you higher in the rankings and potentially more customers.
Think of it as a vote of confidence for your site in the eyes of the search engines. The more you get relative to your competition, the higher your standing. (over simplified answer)
You can backlink yourself, but my experience is whilst clients do it for a while they get fed up quickly, are busy doing what brings in the bacon or sometimes spend a lot of time and energy on it only to realise they were doing it wrong

. Because of this I recommend a long term, drip by drip appraoch to backlinking and get some other bvgger to do it, thats what I do. This is the surest, safest way to move up the rankings and most firms would charge a small monthly subscription with a monthly report.
My big think though is see the big picture first before you start homing in on anything. Every business is unique with its own unique problems. Anyway I'll stop now cos even I can smell the bullpoop.
Hope that helps.
Serving Suggestion:
The best thing to do is go on Youtube and search what is a backlink