.htaccess can be used for lots of things from password protecting , to link redirection and custom seo links and lots lots more here is some good readings http://httpd.apache.org/docs/1.3/howto/htaccess.html you can try these online generators to get you started but not the best way to learn http://demo.scripts.im/SuperSEO/seo-tools-htaccess-generator.html http://demo.scripts.im/SuperSEO/seo-tools-htaccess-password-generator.html
like everything important there is an authority site specually for .htaccess http://www.htaccess-guide.com/ .htaccess file is created with a text editor and can be placed site wide in the domain root folder or with folder and sub-folder validity .htaccess can be placed in any folder of subfolder of a web site in most brief words in your .htaccess you can control access to files, folders, file extensions or place redirect or rewrite rules as well as hotlink protections you can protect your site or individual parts or files from abuse by certain IP or domains or clients you also can control expiration = cache control of files to improve your pagespeed read the guide and start simple because if you have ONE single wrong character or one important missing you may screw your entire server sitewide and produce a 500 error know what you do before doing and test whenever you have done a change in your .htaccess
ht.access file is very important to give the instruction to Google crawler. It is use to change to inner page url name.