Click "Share" button at the top of your screen. (pic. 1)
Pic. 1
A window with sharing options will appear (pic. 2). There are several options how to set it up. Copy the link and share it via an email address or in another way as you are used to.
If you click "Generate a new link", you will get longer link to ensure that your map is shared with higher security. Also, people who only had the old link will no longer be able to access the map except of people explicitly named on the "user list" and people in the workspace. To delete the users from the list, click the trash can button.
Link sharing on new maps is turned OFF by default. Set the Public link ON to make the map visible for public and vice versa. If you set this OFF, you can still share this map with users who are added to the user list as well.
Pic. 2
The map sharing setting will not affect the privacy setting of the map. (pic. 3)
Pic. 3
The recipient of the map link (both a private link or the public one) will see the changes being made in the map by the owner of the map. If he saves the map to his workspace, after that the map becomes his local map and the reference to the original map is lost. That means any changes in the original map will not appear in that currently saved map.
A simultaneous work on one shared map is yet not possible.