The Global Exception Handler is a type of workflow designed to determine the project's behavior when encountering an execution error. Only one Global Exception Handler can be set per automation project.
UiPath Documentation
Exam Topic: Identify and describe the use of the error handling activities such as Try Catch, Throw, Rethrow, Retry Scope, and Global Exception Handler

Rethrow activity is used when additional activities need to be added before the exception is thrown. You cannot specify the type of error to be thrown. Instead, you place Rethrow activity in the Catch handler of a TryCatch, and the type of the error is the same as the type of the previously caught error. Please note, that the Finally block is not executed if the error was rethrown.
Example: Before an unexpected System Exception is thrown, the error is caught in TryCatch activity, a mail message is sent to the IT support team, and then the error is rethrown to end the execution.

Exam Topic: Identify and describe the use of the error handling activities such as Try Catch, Throw, Rethrow, Retry Scope, and Global Exception Handler