DTM has a multi-step approval process. First, a change is funneled into an approvals queue where the details of the change can be viewed. The change can be viewed by clicking the 'Approvals' tab.

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Once approved by an Approver, Approver & Publisher, or Admin level user, the change goes into the publishing queue where it remains until published.

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To publish, an Admin, Publisher, or Approver & Publisher clicks 'Publish Property'. Once published the change is live. 

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A change is always available in the Staging Library regardless of it is approved or published. A change must be approved and published to be available in the Production Library.

More information here: https://marketing.adobe.com/resources/help/en_US/dtm/publish_workflow.html