What is the idea of Users table have a reference to roles table and also have a user_roles table ?

[AdelinGhanaem]

I am trying to figure out the schema for the users/roles/user_roles tables ...

Why does users table have a role_id if there is already a use_roles table? is the relationship *-1 or - ?

 Schema::table('users', function ($table) {
            if (!Schema::hasColumn('users', 'avatar')) {
                $table->string('avatar')->nullable()->after('email')->default('users/default.png');
            }
            $table->bigInteger('role_id')->nullable()->after('id'); // this line here? 
        }); 

And then we also have

 Schema::create('user_roles', function (Blueprint $table) {
            $type = DB::connection()->getDoctrineColumn(DB::getTablePrefix().'users', 'id')->getType()->getName();
            if ($type == 'bigint') {
                $table->bigInteger('user_id')->unsigned()->index();
            } else {
                $table->integer('user_id')->unsigned()->index();
            }

            $table->foreign('user_id')->references('id')->on('users')->onDelete('cascade');
            $table->bigInteger('role_id')->unsigned()->index();
            $table->foreign('role_id')->references('id')->on('roles')->onDelete('cascade');
            $table->primary(['user_id', 'ro

??