Linked contact is a contact that have one or more duplicate contact. If any existing contacts shared the same email, they will be linked.
In the Tact app currently are three types of linked contact,
1. Device Contacts - These are contacts synced from your phone (iPhone contact app)
2. Tact Contacts - These are contacts created in the Tact app
3. Salesforce Contacts - These are contacts synced to Tact from Salesforce
You may have noticed a list of linked contacts at the bottom of a contact details.
1. On a contact details, in the Linked Contacts section, tap on a linked contact
2. Tap Unlink Contact, then OK