WhoID in Salesforce refers to people things. So that would be typically a Lead ID or a Contact ID. The WhoId represents a human such as a lead or a contact. WhoIds are polymorphic. Polymorphic means a WhoId is equivalent to a contact’s ID or a lead’s ID.

What is the use of WhoId and WhatId in Salesforce?

WhatId is a single relationship to a ACCOUNT or OPPORTUNITY. This activity can only be associated with ONE Account OR Opportunity Record. WhoId is a one to many relationship between this activity to one or more CONTACTS or LEADS.

What is ID in Salesforce?

Answer: The SFDC (salesforce.com) ID is a unique identifier of any records located in Salesforce organizations. These IDs exist in 15-character or 18-character formats and are stored in the id field of any Salesforce objects. The 15-character SFDC ID can be converted into an 18-character format.