搜索数据库内容：laravel

Question

public function scopeSearchByKeyword($query, $keyword)
{
    if ($keyword!='') {
        $query->where(function ($query) use ($keyword) {
            $query->where("name", "LIKE","%$keyword%")
                ->orWhere("email", "LIKE", "%$keyword%")
                ->orWhere("blood_group", "LIKE", "%$keyword%")
                ->orWhere("phone", "LIKE", "%$keyword%");
        });
    }
    return $query;
}

'$ query'参数用于什么？函数（$ query）使用（$ keyword）{}是什么意思？

$keyword = Input::get('keyword', '');
$users = User::SearchByKeyword($keyword)->get();

为什么它只是'SearchByKeyword'而不是scopeSearchByKeyword？