Search Engine Optimisation (SEO) is the umbrella term for all the methods you can use to ensure the visibility of your website and its content on search engine results pages (SERPs).
The methods vary from technical practices you can achieve behind the scenes on your website (we tend to refer to this as ‘on-page SEO’) to all the promotional ’off-page’ approaches you can use to raise your site’s visibility (link-building, social media marketing).
When we talk about visibility, we mean how high up the SERP your website appears for certain search terms in the ‘organic’ results. Organic results refer to those that appear naturally on the page, rather than in the paid-for sections.
Building a strong site architecture and providing clear navigation will help search engines index your site quickly and easily. This will also, more importantly, provide visitors with a good experience of using your site and encourage repeat visits. It’s worth considering that Google is also increasingly paying attention to user experience, including mobile optimisation and site speed.
Source: Search Engine Watch