Difference between Laravel's raw SQL functions

I will try to clarify:

DB::raw()

It generates a raw and sanitized SQL string, to be passed to other query/statements, preventing SQL injections. Is to be used with all of the and never alone. And you should never send a not sanitized string to your query/statements.

DB::select(DB::raw('select * from whatever'));

DB::select()

Is for simple selects:

DB::select(DB::raw('select * from whatever'));

DB::statement()

I think it work with selects, but should be used for non SQL query commands:

DB::statement(DB::raw('update whatever set valid = true;'));

DB::unprepared()

All SQL commands in Laravel are prepared by default, but sometimes you need to execute a command in an unprepared mode, because some commands in some database cannot be ran in prepared mode. Here's an issue I opened about this: https://github.com/laravel/framework/issues/53

DB::unprepared(DB::raw('update whatever set valid = true;'));