drupal 7 default table to store form values
You can use Drupal variable system, please read the following article: https://www.drupal.org/node/1111260

You can create you own table, just use hook_schema for it: https://api.drupal.org/api/function/hook_schema/7

If you to get information from your users by form and store it, please check the module webform:  https://www.drupal.org/project/webform

Node table used for storing main information about nodes (it's some type of content). Node can by "Article" or "News", etc. More you can read here: https://www.drupal.org/documentation/modules/node