PEP 621: clarify what the text field for license represents

Author: brettcannon

pep-0621.rst

@@ -248,8 +248,9 @@ The table may have one of two keys. The ``file`` key has a string
 value that is a relative file path to the file which contains the
 license for the project. Tools MUST assume the file's encoding is
 UTF-8. The ``text`` key has a string value which is the license of the
-project.  These keys are mutually exclusive, so a tool MUST raise an
-error if the metadata specifies both keys.
+project whose meaning is that of the ``License`` field from the
+`core metadata`_. These keys are mutually exclusive, so a tool MUST
+raise an error if the metadata specifies both keys.
 
 A practical string value for the ``license`` key has been purposefully
 left out to allow for a future PEP to specify support for SPDX_