WP has a built in gallery. Adding images to a page will create a thumbnail gallery on the page based on the settings you choose.
WP doesn't, natively, have a lightbox type of viewer. If you click on a thumbnail, it will take you to a separate page for the image.
I use the Lightbox Plus plugin. You can see how it works on my site rf-photography.ca. Check the Commercial page or any of the Galleries pages. It's reasonably flexible in terms of how it can be customised.
If you want to get into something like a Simpleviewer gallery or something like that, then you'll need the Simpleviewer WP plugin or a similar plugin for another gallery/viewer type of application.
Keep in mind that Simpleviewer and many of those other types of gallery/viewer applications are Flash based. People with iPads won't be able to see your galleries. Adobe has ended development of Flash so it's basically an obsolete technology. Given the volume of web viewing that's being done from mobile devices, cutting out that audience with Flash may not be the best idea.