Detailed introduction to the definition and usage of HTML thead tag_HTML/Xhtml_Web page production

I would like to ask about this code Why does the comment in say that the first two lines are regarded as the header area? Does it mean that the thead element itself has a default number of lines of two? Or is it for some other reason?
Also, does scope="col" mean to lock the range in the column? What's the point of doing this?
This should be combined with rowspan="2", thead simply represents the table header.

HTML tag
Definition and usage:
tag defines the header of the table. This tag is used to combine the header content of an HTML table. The
thead element should be used in conjunction with the tbody and tfoot elements. The
tbody element is used to group the body content in the HTML table, while the tfoot element is used to group the table note (footer) content in the HTML table.
Note: If you use thead, tfoot, and tbody elements, you must use all of them. They appear in the order: thead, tfoot, tbody, so that the browser can render the footer before receiving all the data. You must use these tags inside the table element.
Tip: By default these elements will not affect the layout of the table. However, you can use CSS to make these elements change the appearance of the table.
Detailed Description:
The thead, tfoot, and tbody elements give you the ability to group rows in a table. When you create a table, you probably want to have a header row, some rows with data, and a total row at the bottom. This division gives the browser the ability to support table body scrolling independently of table headers and footers. When long tables are printed, the table header and footer can be printed on each page that contains the table data.
Example: HTML table with thead, tbody and tfoot elements: