NextGEN gallery plugin is one of the best photo gallery plugins available for WordPress. NextGEN is very flexible yet simple to use. For instance, except images resizing you can arrange them in your favourite way or according to file names. One of the very useful options is watermark stamp, which means that your images can have copyright note automatically stamped with every new image added to gallery. It is possible to use as watermark not only text, but also an image. Transparency levels of both text or image used for watermark can be determined in gallery management panel of NextGEN plugin.
Most powerful feature of NextGEN gallery is shortcode. It means, that after creation of a gallery it can be placed on whatever page by simply adding to the page shortcode like: [ nggallery id=x ] where id is number of a photo gallery. WordPress recognizes this code as a command to place photo gallery with id number given in square brackets of shortcode. This way after gallery is prepared, it’s location on a website can be quickly and easily changed.
In general, in WordPress terminology, shortcode is a piece of code (macro code) placed between square brackets. After plugin installation WordPress system gets information concerning new shortcodes available. So, you can place whatever code or text between square brackets and add this to page text, but nothing happens as long as this code has no meaning for WordPress system. Actually NextGEN shortcodes are a kind of interface between users and WordPress system. They are constructed in a way so you can understand them easily, which means they are easy for customization too. Only simple short commands/codes are supposed to be between square brackets, however the short commands/codes usually mean very complicated tasks undertaken by WordPress system.