To restore a site on the same or different machine using the content db backup follow the steps given below:

Follow these steps :

1. Create a new Web application on the destination server.
2. Go to central admin –> content database . Click on the new web app content db.
3. Remove the content db.
4. Go to SQL server mgmt studio and create a new db with the same name as the content db backup you are having.
5. After creation right click restore. Choose the backup file location. From the options tab choose ‘overwrite’.
6. Restore this db backup.
7. Go to central admin –> content database again and select ‘ add a content db ‘ to the web application.
8. specify the name of the restored db.
9. Done

Enjoy!!!