www.whatiscopyright.org/
en.wikipedia.org/wiki/Copyright
www.law.cornell.edu/wex/index.php/Copyright
en.wikipedia.org/wiki/Intellectual_property
www.eff.org/IP/
www.copyright.gov/
As to pictures someone takes (they are actually copyrighted AND intellectual property as soon as said person takes them- ie All my PTA/PTO, school pictures I've taken ARE copyrighted to ME only)
That said, registering copyright is a good method of having irrefutable proof that the photos are yours. This is an excellent idea if you have plans of selling your work as individual or a whole, especially if you have printed material as for the web, if you put "Copyright & copy Your Name (or business name)" then it is recognized through most international agreements. (You must have both the word and symbol on your photos, not just your site.)
However that is only the case with those contries who have signed with international copyright regulations (laws) and may not apply to those places which do not recogized the international copyright agreement.
(Inherently the originator of the idea (written or photograph) has copyright)
The "poor man's copyright" is to snail mail a copy of the photos or written text to yourself. Once you receive it do not open it the post office stamped date is what you require for "proof". If by chance you need to defend yourself against a copyright infringement case then you can have a Judge of the case open the said envelope. But this is not 100% recognized and does not guarantee your copyrights.
Just remember for every photo or group of photos you want officially copyrighted you must refile with the Gov and pay that fee everytime. It can get quite expenisve for just personal photos.