Field_data_commerce_line_items vs commerce_line_item in Drupal Commerce

Question

I realized that in my database there are two tables with similar names: field_data_commerce_line_items and commerce_line_item.

Can someone explain the purpose or reason for their presence? I mean the difference between the two.

I understand that field_data_commerce_line_items is a reference field in the order that refers to a row in the commerce_line_item table on the data_commerce_line_items.commerce_line_items_line_item_id = commerce_line_item.line_item_id field. However, the overall picture still does not work out.