Zoho mail offers ‘Archive’ feature, using which you can protect your old, unused email data for reference at a future date. When you move a message to archive, the folder structure is retained in the Archives, which makes it easier for reference and retrieval.
Auto-Archive is the process where archival process is triggered based on the Archive Options

The messages will be moved to the Archive folders. A directory tree will be created similar to the directory tree in Inbox, if it does not exist already.
You can archive the messages in the folder using the Archive Folder option available in the Right click. Right Click on a folder and select Archive Folder. The following options will be available to clear the messages in the folder.

The messages will be un-archived and moved to the respective parent folders under inbox.
You can also un-archive an entire folder. To un-archive a folder, right click and choose un-archive folder.
You have an option to include Archives in your search. You can include Archives, if you believe that the message you search may be in your Archives. However, including Archives in search might take a longer time depending on your Archive size.
You can optimize your search by choosing to exclude Archives and thereby save time. Archiving messages also optimizes the storage space in a long run.