In many places we have three buttons to begin the editing of content:
New - This will open the editor with a blank record. There might be some of the fields that are pre-filled with default values, but most of the input fields will be blank. There will only be a button called 'Save'.
Edit - This will open the editor with all the values filled from the existing record. The user can choose between 'Save' and 'Save New Copy' when saving the data.
Copy - This will also open the editor with all the values filled from the existing record. The title or Id column will include the words "Copy of:" and there will only be a button called 'Save New Copy'. This option eliminates the possibility of accidentally clicking 'Save' on changes you intend to become a new section, page, blog post etc.
Choosing 'Edit' is the instance where you can choose between 'Save' and 'Save New Copy', so let's look at what the difference is.
When to choose 'Save' and when to choose 'Save New Copy' in Edit mode.
Save - when you click this button it saves the changes you have just made to the section, page, blog post etc. This button is available when creating new records or making changes to existing records.
Save New Copy - it makes no changes to the original record, but instead saves a new copy of the record you are editing, with the additional changes you just made. This button is only available when you edit an existing record.
Example: You are editing a section that says: "I have an idea". You make a change to the section saying: "I have a GREAT idea" and click "Save": Your section has now been changed from "I have an idea" to "I have a GREAT idea".
You do the same as above, but instead of clicking "Save", you click "Save New Copy". Your original section of "I have an idea" is still there unchanged, but you now have an additional section almost identical to the first with the only difference being that this one is saying "I have a GREAT idea". (Also the system has assigned the section a new unique id for linking purposes). Even if you don't make any changes before clicking the Save New Copy button you will end up with two copies of the same content.
How to use this feature
This feature is great to use if you have a section where you like the initial set up and you want to create a new section that looks very much like it but with a few changes. This will get it set up quickly.
However, for changes to existing sections you should always click "Save" so you don't make additional copies of the section as described above, unless it is what you intend to do.