To search for a pattern across all project files, or other non-project files, use the Search Files command. See: Search Files. The Search Files command is similar to the Search command, except you can specify what files you want to search. The results of the search are placed in the Search Results window. The search results also contain hidden information called source links.
If you are just looking for single, whole-word references across your whole project, the Lookup References command is much faster. See: Lookup References.
The Search Project command searches for text or keywords across all project files. This command works the same as the Lookup References command. The only difference is that each dialog box has its own persistent state.
The project search bar is used for searching across the whole project. It is a powerful way to perform a keyword based search to find name or word fragments within a given number of lines of context. To show it, select View > Project Search Bar.
If you want to search your whole project as though it was a web site, then use the Search Project command. Using keyword searching, you can find any combination of terms or symbol name fragments that occur within a specified number of lines of context. See: Search Project.
The Search Web command (Ctrl+Alt+W) searches for the identifier at the cursor position using your web browser and your preferred web search engine. See: Search Web.