What data gets sent to the server when I submit from a form?

I would like to issue a submit from my form and have data sent back to the server. Is the only data sent to the server that which appears within the form ( xxx fields etc.) or will the data such as that in the input fields yyy also be sent to th开发者_Go百科e server?

<form action="/adminTopic/Edit" method="post">   

xxx

</form>

yyy

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Only the fields within the form will be submitted, in this case only xxx sent back to the server