[Laravel][ATOMIC] DB::transaction, DB::beginTransaction

 DB::beginTransaction() will only begin a transaction, while for DB::transaction() you must pass a Closure function that will be executed inside a transaction.

So this:

DB::transaction(function() {
    // Do something and save to the db...
});

is the same as this:

// Open a try/catch block
try {
    // Begin a transaction
    DB::beginTransaction();

    // Do something and save to the db...

    // Commit the transaction
    DB::commit();
} catch (\Exception $e) {
    // An error occured; cancel the transaction...
    DB::rollback();
    
    // and throw the error again.
    throw $e;
}

As you can see, DB::transaction() is a "helper" function to avoid writing code to catch errors, begin a transaction, commit the transaction, and optionally rollback (cancel the transaction) if an error occured.

If you have a more complex logic, or need an specific behaviour, you will manually build your transaction; if your logic is rather simple, DB::transaction() is the way to go.

As for DB::commitTransaction() and DB::rollbackTransaction(), I can't find information.

It's a good practice to check the source code of the things you use, because you will learn how they are written, as well as how to write. Here's the file with the source for these methods.