Keywords along with title tags are the key to SEO. Though keywords and title tags literally are the same as far as I know they are slightly different(for a blogger). Keyword is actually one of several META tags. Keywords are added inside the META tags into the html code inside the “head” tag of your homepage and can include all title tags plus any additional keywords that are used for the whole content of your site. Title tags are keywords that vary for each post in your blog. Title tags essentially refer to one particular post and can be unique for each post in your blog. Google search engine now ignores META tags, hence title tags are very important for its search results. Google search results(SERP) are decided with title tags. Other search engines mostly use META tags.
SERP stands for search engine results page. It is a list of web pages returned by a search engine in response to a search performed using a list of keywords. The best way to improve your site’s SERP rating is by using Meta tags and title tags. I would say title tags give better results for Google search engine as Google ignores Meta tags. For Yahoo and other search engines both Meta tags and Title tags work well. For SEO(Search Engine Optimization) is very important for the sucess of a website. SERP affects SEO and can be improved by building backlinks. For backlinks I recommend registering to webmasters like Linkreferral and also a few traffic exchange sites, a list of which is mentioned here.