Gzip is a method of compressing files (making them smaller) for faster network transfers.It allows to reduce the size of web pages and any other typical web files to about 30% or less of its original size before it transfer.A file allows you to restrict the access of search engine robots that crawl the web and it can prevent these robots from accessing specific directories and pages.
Code to text ratio represents the percentage of actual text on a web page compared to the percentage of HTML code, and it is used by search engines to calculate the relevancy of a web page.
A higher code to text ratio will increase your chances of getting a better rank in search engine results.
Backlinks are links that point to your website from other websites.
They are like letters of recommendation for your site.
It's important to carry out keyword research to get an understanding of the keywords that your audience is using.