Basically, this feature allows you to make modifications to a launched Campaign while messages are in the process of being deployed. These changes will then be applied to all un-sent messages.
Think about we realize that we need to modify the subject line for some reason or any other content, we would suspend the Campaign then change the subject line and run the campaign again with the Pick Up Changes option.
That would avoid to cancel the campaign and create a new one.
Also, the only exception to this rule can be an Event-triggered Campaign. In that scenario, we wouldn't need to first suspend the Campaign before running Pick Up Changes.
