On page search engine optimization is how you select keywords and optimize your website content for them. You need to select keywords that are highly searched in popular search engines, but where competition at the same time is weak. You need to select keywords that also fit within your products and theme of website.
Classic search engine optimization would include ensuring the content of pages have keywords in titles, headers and content. However, even if done well,
the algorithms between search engines vary, and it is not sure you will score the same in e.g. Google and Yahoo.
Off page search engine optimization is where the big differences comes from. You will want to get backlinks (or inbound links if you will) to your website with anchor text matching the linked pages and website theme. This is also something you have to determine when comparing competition for a search phrase.
A
keyword research tool can help you select optimal keywords, determine competition strength and optimize pages.