How Can SEO Content Help Increase Traffic to a Website?

Heather works for a website owner that sells tickets to special events and movies.  She has been working for him a little over 7 months.  Heather works from home and writes SEO content for the website owner.  She has a couple of other clients that she writes for also but the ticket site is her main focus.  The website owner told her that since she has been writing his traffic has increased steadily each month.  She makes sure she is putting relevant content and keywords that help the search engines locate the site.  She has been very busy writing and may have to drop one of the other clients because she has gotten so busy.