What is SEO?
Search Engine Optimization or SEO is the process of tuning your site so that Search engines like Google or Bing prefer it over other sites and show them first in results.
Why be “SEO friendly”?
Being SEO friendly means you have more chances of ending up at a higher rank on a relevant search query. Higher Ranks would mean your site shows up on the first page or better first rank, thus having more likelihood of being seen and checked out by users bringing in more traffic to your site.
What do SEOs like?

Search engines need to make sure their organic as well as paid search results are as user friendly as possible and the result contents need to be valuable and in-line with the search query. Thus as a general principle they prefer user friendly and trustworthy sites (e.g. fast sites or mobile friendly sites with no plagiarized content) and sites which are easy to comprehend by their robots to see if it has the right content (e.g. reading text processing for semantics and alt text for images).

Search engines do not explain the ranking algorithm but they do suggest the changes for site optimization and other things can be inferred from experiments.

Should I invest in SEO or PPC?

SEO helps you rank better organically and PPC is for paid traffic. Ideally, you should balance out and invest in both for organic and inorganic traffic coming to your website.

Why isn't my site ranking on google?

There could be a number of reasons, please refer to your site’s audit report for more information.

There are only a few spots and everyone wants them. You can, however, put your best foot forward and make sure the users who are looking for your offerings do see your site in their top results, instead of your competitors.

How long does it take for changes to result in a good rank/first page?

SEO is a long term activity and changes take time to show effect in rankings sometimes from 4 to 6 months. New sites may take even longer than a year.