In my Drupal 7 site, users will fill a form. After some search i found that Webform is very easy to create forms. I created one.
When user submit the form, a php file will query the MySQL database and find relevant records. My question is which module or core function is suitable to easily display these results with good looking objects??
If I understand correctly you are trying to use the webform module as a search engine. However this module was meant to help you make forms to uptain information, like a contact form or surveys.
If what you want is something like a search engine I would suggest using the default search engine that comes with your drupal install. If you want a advanced search function based on multiple fields, so a filter system, you could for instance use the downloadable views.
Using views you can easily make a good looking overview for instance for one or more content types. By exposing the filter criteria fields, users would be able to query the database.