Understanding automatically generated key-value pairs

Scroll down to the latest lines of the document in the web-based editor and you will see new key-value pairs that were not part of the original document. The following screenshot shows the last lines in the embedded JSON editor:

The following lines show an example of the new key-value pairs. Note that many values will be different in your case:

    "_rid": "prUNAKtPjRoFAAAAAAAAAA==", 
    "_self": "dbs/prUNAA==/colls/prUNAKtPjRo=/docs/prUNAKtPjRoFAAAAAAAAAA==/", 
    "_etag": "\"22007fea-0000-0000-0000-5b86dbd60000\"", 
    "_attachments": "attachments/", 
    "_ts": 1535564758 
} 

Cosmos DB added the following keys to our document, which start with an underscore (_) as a prefix and contain system-generated values for the document...