Use this pattern to poll an external system, that is, to periodically request data from an external system and take an action when some condition is met with the returned data.
As an example, think of an integration with SAP, where a process submits an invoice to the SAP system and has to wait for it to be approved in SAP before continuing.
When the process is executed the following occurs:
The Automatic Activity submits the invoice to SAP;
The Wait activity holds the execution of the process;
When the timeout occurs, the Wait activity is tentatively ended by executing the OnClose callback action: it only ends when the invoice is ok, otherwise the waiting continues until the next timeout (one more day from the current date and time).