He says that in the unordered-map ordering changes

He says that in the unordered-map ordering changes.I am not able to get what type of order he is talking about.

Here he means that if you were to make a new unordered map and store the same key value pairs, the ordering of storage is most likely to differ in chained hashing. Whereas, if you store the same pairs in newly created map, it being a self balancing red black tree internally, will store the elements in same fashion everytime.