The dataset UID (Unique IDentifer) is the 4x4 of alphanumeric characters at the end of the dataset url.
Every dataset, working copy, chart, map and user account is associated with one.
For example, this is a public dataset on Opendata.socrata.com with a UID of 6v2k-v9qc.
For tabular datasets that have an associated Primer page, this URL will direct you to that page. To go directly to the table view, add"/data" to the end of the URL.
Tip: if you have the UID of the dataset/view/visualization by using the shortcut on that domain: https://DOMAIN/d/4x4