First of all, just having a website does not guarantee that web surfers will find your page. With literally millions of pages on the internet, most people rely on search engines to serve up meaningful results based on key words. It is very important that these search engines...predominately Google, Yahoo and Bing...know about the existence of your company's website. This is a relatively easy step.
Secondly, for the search engines to properly index your site, special code must be inserted into each page of your web site, which uniquely describes its content. While the indexing and ranking algorithms are closely guarded "secrets", this is an important process.
Lastly, your site has to possess a relevance on the web. What this means is that the more sites that link to your site, the more relevant that it is. This is sometimes the trickiest part of the optimization. It is important to make sure that the sites that link to your site are relative, as some search algorithms are beginning to penalize a size for having hundreds of "not-so-relevant" sites pointing to yours. Rest assured there are "ethical" means to improve your site's ranking despite this.