This was all free information I found online in less than an hour, that gives me some great ideas for content, partnerships and potential tools to build into my site to be relevant and useful to my target audience. Of course this is just some quick loose data, so I'll emphasize again: be careful where your data comes from (try to validate when possible), and think about how to use your data wisely.
The leading search engines, such as Google, Bing and Yahoo!, use crawlers to find pages for their algorithmic search results. Pages that are linked from other search engine indexed pages do not need to be submitted because they are found automatically. The Yahoo! Directory and DMOZ, two major directories which closed in 2014 and 2017 respectively, both required manual submission and human editorial review. Google offers Google Search Console, for which an XML Sitemap feed can be created and submitted for free to ensure that all pages are found, especially pages that are not discoverable by automatically following links in addition to their URL submission console. Yahoo! formerly operated a paid submission service that guaranteed crawling for a cost per click; however, this practice was discontinued in 2009.