In Sitecore 7 MVC, my understanding is that partial views are represented by using Razor declarations such as @Html.Sitecore().Placeholder("some_thing") in a .cshtml file.
In this context, what does the argument "some_thing" actually represent - is it something located in the Sitecore instance? If so, how can I locate the thing that "some_thing" represents within the Sitecore database?