Tazer has spotted the 'typo' in Note 2 clause 14.1.
In 2 places it mentions 'PEES' - this should be 'PESS'.
The definitions given by Shimon are correct.
A correction for this typo is included in the current Committee Draft of Amendment 2 of 60601-1. See IEC CH/62/1_17_0057.
The expected publication date of Amendment 2 is the end of 2019.