At this point any scan data that you have collected this turn is shared with any empires that have access to your empire's scan data. Shared data is merged with the recipient's map using the "most visible" status of each shared sector. For example, if a sector is visible to you, but has only scanned status on the recipient's map, then it will appear as visible to them; however, if the shared sector is stale on your map, it will still appear as scanned on the same recipient's map.
Only scan data that your ships collect directly will be shared with the authorized recipients, i.e., any data given to you by empire A will not be given to empire B.
Sharing scan data does not share ship designs, portal navigation data, or message contacts.