Keywords
Keywords, long-tail keywords and keyword lists are the ways that Search Engines match what you are looking for to the existing web pages. From the pages that contain these search-keywords the Search Engine makes up a list, which is in descending Relevance sequence – but also in descending page Ranking. These results are presented as a Search Engine Results Page – SERP, or often pleural SERPs.
Relevance will be determined, mostly automatically, by the word content including titles and keyword counts. Page Ranking is more obscure and includes such things as the number of outside links pointing to the page, the ranking of the sites where the links are coming from, the relevance of those other sites, the age of your site (older is better) and possible negative factors, such as if your host has any connection to other sites which have been blacklisted for spamming.
Google keyword tool – will show keyword search result statistics indicating (i.e. this is not precisely accurate, statistics are only indicative) how often the given word/phrase and related word/phrases are searched for and what the competition is like. Generally the more words in a phrase, the less often it’s searched for and the lower the competition is.
Contrasting the lower volume of searches for a longer keyword phrase (long-tail keywords) is the supposition that, as people refine their search to get more targeted results, they are more likely to buy when they click through to a sales page - all other factors being equal, or course. So you get a combination of less competition, lower bids (Cost Per Click), and more chance of selling – higher Conversion Rate. This is why there is so much interest in long keyword phrases, and in researching to get the best list of keywords.
Keyword tools:
Google AdWords’ Keyword Tool shows results indicating* how often the given word/phrase and related word/phrases are searched for and what the competition is like.
(*i.e. this is not precisely accurate, statistics are only indicative)
ttp://www.goodkeywords.com free keyword research tool
http://www.wordtracker.com/ take the free trial option