Search engines and finding your readership
Once you have your web content, organized into the pages of a web site, and hosted on a web server, well, then what?
If you were to open a knick-knack shop on a side street (because the rent is cheaper), are you likely to automatically get customers? It's a side street, so there isn't much foot traffic, hence you wouldn't have a lot of visibility. What do you do? You advertise, that's what. Call the Yellow Pages people, and other local advertising outlets, and get an advertising campaign rolling. Advertising gives attention to your knick-knack shop, and hopefully it draws customers because the rent is due every month and you could be out on the street real quick without customers.
Likewise, on the Web if you don't tell anybody about your site nobody will come. You can write all you want, but if nobody reads it then you're just talking to yourself. What you want, for your words to have an impact in the world, are visitors. Often the more traffic the better.
Most people find web sites of interest through Search Engines. A search engine is a specialized web site that lets you search for other web sites, and it returns you those web pages that match whatever you're searching for. No doubt you've used Google, Yahoo, Alta Vista, Lycos or the like to search. Those sites are what is meant by "search engine".
Another way people find sites is through "direct linking", which is simply when one web site contains a link to a page on another web site. Often web site creators put in a page listing related web sites.
Of interest is the order that search engines return the results to queries. If you're going to write a web site about "Digital Cameras" then you want your web site to show up high within the search engine results whenever someone types in "Digital Cameras". There are many arcane arts involved with affecting the results a search engine gives, and one of them is those direct links. It's obvious that a site which has many links pointing to that site must be a popular site, so the search engines will rank such a site more highly than other sites on the same topic.
You can also do advertising. This takes many forms, but the purpose is the same as always. To get a message presented to the public, drawing them through your doors.
The last attribute to think about are your readership. Just like you are my readership, you wish to find readers for the material you want to write. It is the readership that gives your web site purpose, as it is them to whom you are writing, just as it is your enlightenment that gives purpose to my writing this web site, and why I am writing to you now.