That's really just the basic stuff, any webmaster should include meta tags/alt tags/SEO friendly URLS just normally, it's just something I personally add to a design, so I don't have to optimize it later, but I don't have to think 'oh i need to add alt tags here', I just do it.
All SEO is "on-page" technically. This is where you optimize your keywords, description, etc. All your meta tags basically. It also includes HTML validation, SE friendly URLs, logical page order. Anything that you can improve by editing your html/php etc The rest is just link-building which is not really SEO because there is no "optimization" involved in it
Link building is very important to rank better. With High PR links even bad articles can rank better. With no links even the best articles will have no place in search engines. What SEO Firms Do?