We mean that your content is optimized when it is fully set up under a keyword or phrase.
Important things the engines look for in order to rank your page are your title and your page heading and also occurrences of your keyword in your text.
Other things you can do are :
name your top image as the keyword and set the alt tag as the keyword as well.
These steps help strengthen your content as being all relevant and focused on your keyword.
These steps are very rudimentary. You really need to run an optimisation report on your site using a free tool, to get more in-depth guidance on optimising your content.