Search engine optimisation is the techniques which are applied to both on and off web pages, to increase their visibility on the search engines, such as Google, Bing, Ask and Yahoo, there are many others out there but these (at least in the UK) are the major ones to focus on.
It is something you can do yourself, provided you have a lot of spare time, more likely you would use an SEO Company to do this work for you. A good SEO company, will be up to date with all the latest techniques and focus initially on analysing your competition and starting the keyword research, this is absolutely essential before any other search engine optimisation work starts, as it will form the foundation for the whole seo campaign.
If you do not already have a website, a good seo company will be able to help you with some fundamentals, including chosing the best URL for the websites address and making sure that the template or design you start with is tweaked appropriately for being found in the search engines.
Many blogs also exist, but again it can be difficult working out which advice to follow or not, there are many outdated seo techniques out there, however a lot of companies are still offering them simply because unwitting customers will keep paying for them, in the false hope that it will help their web rankings.
If you want an attractive but easy to maintain website, the easiest way to do it is with a CMS such as Wordpress, these sites can be optimised with the use of plugins, however if you really need to be competitive, in my experience, proper html pages are better.
