When migrating a site, list or library that has content already present at the destination, it’s possible that an item will already exist at the destination. In that case, 4 options will be offered to you.
Copy and Replace: Replace the item or document in the destination list or library and all its versions with the item or document from the source.
Don’t copy: No item will be changed in the destination list or library.
Rename: This will copy the source item with a new name in the destination list by appending a number after the name (i.e. myFile.txt will become myFile (1).txt).
Copy if newer (incremental copy): This option will only copy items that have a newer modified date than the item at the destination. If versioning is enabled, Sharegate will add the new versions from the source at the destination. If the versioning is disabled, the destination item will be replaced. Note that if the item at the destination is deleted or moved under a different hierarchy, the incremental copy won't find any match and will create a new item. Note that when using the insane mode on Office 365, all versions at the destination will be replaced by the versions from the source because of a limitation in the Azure Import API.
The options that are offered in interactive mode:
The options that are offered in silent mode are:
Copy SharePoint Content
Copy Site Objects