Yes, this is going to be very basic, as I've found alot of mythology about the internet and how search engines work .. and while I am by no means an expert (though I do get paid for this .. so I am a professional) .. I would like to provide some information, that I have had to share on many occasions with new clients.
- Google takes a copy of your website every few weeks (depending) and stores it in their huge data-centre.It does not go out looking for the results when you ask .. it's already go the results
- Pictures look good to your visitors, but have little affect on your search ranking. (There are titles and alt-tags that do help, but Google does not care what type of photo you have). This includes flash files (urghhh) ..
- Websites are search by 'robots'. Programmes written to go through the HTML code and 'read' it. You can tell therobots not to go through your site if you really want.
- Meta-keywords are NOT used by Google and have not been for a long time. Have a look at Googles meta-tag page.. it does not even mention them any more. So if an SEO expert suggests he will have a look at your meta-keywords .. hit him with a meta-stick.
- Meta-descriptions are still used, but mainly to generate snippets, and not so much for ranking purposes. If you're going to use them .. make sure they are done properly. If you don't know what they are .. all the better.
- Content is king- since the last major update of Google (panda), the actual content of the site has become so important. Previously there were little 'tricks' that could be used to 'load' the site with keywords .. this has cause a proliferation of content, again proving that by shifting focus onto content, it just creates more content, alot of which is generated purely for ranking purposes, and the rise of content-providers.