Post Type names should have max 20 characters, and only contain alphanumeric, lowercase characters, underscores in place of spaces and letters that do not have accents. Reserved names: post, page, attachment, revision, nav_menu_item.
If you are unfamiliar with the advanced post type settings, just fill in the Post Type Name and Label fields. Remaining settings will use default values. Labels, if left blank, will be automatically created based on the post type name. Hover over the question mark for more details.
Deleting custom post types will NOT delete any content into the database or added to those post types. You can easily recreate your post types and the content will still exist.