SEO
SEO means making your site easy for search engines to understand, so it shows up when people search.
In a simple example
A bakery page that says clearly who you are, where you are and what you sell is easier to find than a page of pictures only.
Why it matters to you
Most new visitors come from search, so clear pages bring free visitors every day.
Do not confuse with
SEO is not advertising. You do not pay for each visit.