Search engine optimization. Basically just positioning your website to appear prominently in the search engine results when people are searching for your target keywords. For instance, you might want your site to appear at the top if people are searching for "fantasy map artist" or something like that. If it's just a hobby site, then this probably isn't very important. But if it's a commercial enterprise, then you definitely want to get traffic from search engines. Assuming you target the right mix of keywords, search engine traffic tends to convert better than other marketing channels (except for referrals) because people are actively looking for what you offer.