The ->validated() method returns information from your request that actually underwent validation. Let's use a quick scenario:
dd($request->input());
// ['name' => 'John', 'middle_name' => 'Smith', 'last_name' => 'Doe']
If you have the following rules:
$rules = ['name' => 'required', 'last_name' => 'required'];
Then, after running validation, calling ->validated() will return the following:
dd($request->validated());
// ['first_name' => 'John', 'last_name' => 'Doe']
Notice how middle_name is missing? It was not included in the validation rules, and as such is stripped out.
You can read the full documentation here:
https://laravel.com/docs/8.x/validation#working-with-validated-input
Note: If you're validating everything in your $request, i.e. first_name, middle_name and last_name, then you can use $request->validated(), $request->input() or $request->all(); they will all be the same.