The Translation Management module by default doesn't take revisions into account.
When content is edited, the content editor can choose whether or not a new revision is created and if this content is in draft status (the content is not finished yet) or published.
If a new revision/content is in draft it should not automatically be sent to the translation service. This module allows nodes and draft revisions to be saved in a translation queue.
On the translation dashboard nodes/revisions that a queued for translation can then be selected and sent for translation.