It is a common mistake of thinking that search engine submission is same as search engine optimization.
"Search Engine Submission" refers to the act of registering your web site on search engines. In another way of saying getting your website listed on search engines.
Getting listed does not mean that your web site will be on the first page of search results; however, it means that the search engines know your pages exist.
"Search Engine Optimization" or “Search Engine Placement” refers to the act of changing and verifying your site content and structure so that it may rank well for particular terms, especially with crawler-based search engines.
Every search engine uses its own unique algorithm to index and rank web sites. Search engines' algorithms weigh various factors, such as HTML scripting, a page design and links to rank pages in their search results. Search engines hope to give their visitors the most relevant results by constantly refining and improving their algorithms.