Different people have their different definition for the SEO as some define it as relationship with Google trough ad words, Search console and analytics. Some take it as the ability of other sites to get to your effective content. SEO is magic that the SEO experts can do only according to some people.
If we consider its actual definition then it is a combination of content, technical fundamental, user experience and let the Google help you. With the effective SEO we help the Google and other search engines to recommend you for great user experience.
So there are 3 technical fundamentals that can help you for better search engine
Responsive and creative design of your website not only helps you to impress the user but also to Google. Responsive designs means that the design and experience of your website that respond according to the size of the device of user. Even Google also announced mobile friendliness as the important factor in the Google listing for ranking. Responsive design helps you to keep the content at one URL unlike the mobile site URLs. So it is the essential tip to have the better search engine optimization.
HTTPS that is stand for Hypertext Transfer Protocol Secure uses the Secure Sockets Layer (SSL) to encrypt information being sent and to ensure the security of the information. So the SSL certificate not only brings security for the users that are on your site but also help with SEO. In 2014 Google announced the use of HTTPS as the ranking signal while displaying the search results.
However security is not the big factor for SEO but if two similar sites are there then one is secure then Google give it higher rank so secured site will come on the higher rank in displaying Search results.
Accessibility is also technical factor for the better SEO as even the SEO experts focus a lot on the accessibility of the website.
In accessibility for instance requires the ALT text on the all images that will appear in the blank box where the image would normally be to tell viewers the content of that image. As the user will click then text will get crawled and then will be displayed in the search results.
There are many tools for enhancing the accessibility of the website like the site map, proper use of header tags, bread crumbs that can enhance the user experience and can lead to higher results in the Google search results.