My mom use to ask me about my work from time to time. It’s quite easy to explain her as a permanent user of Google though she mostly search for films/video. She knows what is S/GERP (search engine/Google ranking page). What is always new to her is the very idea one can influence on SERP. That is exactly what SEO about!
It’s plain to see why to get your website ranked in Google Top. The higher your website ranked the more users will visit your website. Positions 1-5 generate 80-90% of keyword traffic depending on the keyword difficulty and niche. Though there may be exclusions – say while searching a family villa in Greece some users will skip the 1st SERP filled with trip-ad.visors and similar portals. The ones who own/run those villas will probably occupy the 2nd and even 3rd SERP. So for such a website top10 would be not necessary.
Some SEO guys sometimes promise a certain position in Google Top. I usually say one should be in Google Board of Directors to be absolutely sure about it. So as for me I guarantee improvement of ranking by the target keywords. It means the keyword should be relevant and website should be already ranked when I start my work.
SEO consists of two parts – on-site (website itself including technical points) and off-site (backlinks). These parts should go in accordance.