multipart/form-data is a mime part used in the enctype form attribute to encode the keyword and corresponding state of input field before sending into the body of the HTTP request
A formdata when send via XHR is encoded in this format
------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="t"
cats
------kYFrd4jNJEgCervE
Content-Disposition: form-data; name="q"
fur
------kYFrd4jNJEgCervE--
This encoding could have been created with this form where cats and fur are the data entered in the input field t and q
<form action="/find.cgi" method=post enctype="multipart/form-data">
<input type=text name=t>
<input type=search name=q>
<input type=submit>
</form>