In a helpdesk, a contact is a customer who sends in support tickets through the many channels you have enabled in Freshdesk. They can submit tickets, check their ticket status, read articles, participate in forum discussions, etc.
When you delete a contact in Freshdesk, their information is not entirely purged from the system initially. Instead, the system will move the contact to the "Deleted Contacts” list in Freshdesk, and you can restore these contacts as and when needed.
Note: Any future communication from a deleted contact will be directed to the SPAM folder.