Select statement is used to select columns that you want from your database table:

DB::table('users')
            ->select('name', 'email as user_email')
            ->get();

Through method is actually alias to transform() from php Illuminate\Support\Collection; . Be aware that through() is only possible to call on Pagination instance (after querying with paginate()): AbstractPaginator

The transform method changes each item in the collection:

$collection = collect([1, 2, 3, 4, 5]);

$collection->transform(function ($item, $key) {
    return $item * 2;
});

$collection->all();

// [2, 4, 6, 8, 10]

So you can decide how your data will be look like before passing it to the response (like View). It's very similar to API Resources or Transformers (Fractal pattern).

How Does Real-Time Table Filtering Work