Organic search is search results that appear without paid advertisement influence. They are ranked by search engines based on a variety of metrics such as relevancy, quality, popularity, etc.
The main goal of SEO or search engine optimization is to influence organic search in a way that your page appears higher in the results. It is important since users do not go further than the first page of results and they are more likely to convert than on pages from paid ads. In the long term, it is also cheaper than a pay-per-click advertisement.
It does require a lot of effort to rank higher though. SEO experts have to optimize the following to get noticed by search engines:
Mobile Optimization
The website has to have a mobile version that will provide a better experience to those who visit from phones or tablets (they bring around 55% of traffic nowadays).
Linking
It is important to have relevant linking on the website and have other websites backlink to you.
Loading Time
Users are not likely to wait more than three seconds. Search engines present results that will satisfy users.
Content Quality
Content quality is one of the main factors. You may have a speedy website, many backlinks, and beautiful design but if the content is bad, irrelevant, or copied, search engines will not let that pass.