Node Theme is used to enable easy switching to another theme based on the path. Any site path can be controlled, not just nodes, but the name is carried over from D6.
Enabling Node Theme for the first time will add a table node_theme to your database. This table is used to match paths and the desired theme. You can select a theme for a node on the node form, or you can create and maintain any path on the Node Theme manage page (admin/config/node_theme/manage).
If a page is requested by a raw path that does not exist in the table, Node Theme will check for the alias path, if any, in the table. If the page request is an alias that does not exist in the table, Node Theme will check the table for the raw path. If no entry is found, or if the theme mapped to the path is not active, Node Theme will do nothing. Otherwise, it will present the requested theme as a custom theme, which switches the display to that theme.