What does action=./?> in the form mean? Thank you_html/css_WEB-ITnose

There is a paragraph in a microcontroller web server program as follows:

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./ represents the current directory, ? represents the query string is empty

Submit to this directory 's default homepage. .

If it is action="?", it is submitted to yourself

./ represents the current directory, ? represents the query string is empty

Thank you very much 3 people Guidance, I probably understand. But just like the action="?" written on the second floor, this is also a question I want to ask you: when should the double quotes here be included, and when should they not be included?

action="" //Generally it can be empty, the double quotes here must be there, indicating that the bill of lading is submitted to itself (that is, the current page is processed)

action="a. php" //is a.php submitted to the current directory for processing

Thank you very much for the 3 people's advice, I probably understand it. But just like the action="?" written on the second floor, this is also a question I want to ask you: When should the double quotes here be included, and when should they not be included?

It is standard to write with double quotes, and it is not wrong to not use them~

Thank you very much for your advice. I searched several books to no avail, but found the answer here. Thanks again for your advice.