A custom model allows you to add your own methods, add relationships and so on.
The easiest way to use your own custom model would be to extend the
default Spatie\MediaLibrary\MediaCollections\Models\Media
-class. Here's an example:
namespace App\Models;
use Spatie\MediaLibrary\MediaCollections\Models\Media as BaseMedia;
class Media extends BaseMedia
{
...
In the config file of the package you must specify the name of your custom class:
...
'media_model' => App\Models\Media::class
...