Can you explain the five elements of an assurance engagement?

Five elements are:

• A three party relationship.
• Subject matter.
• Criteria.
• Gathering of sufficient evidence.
• Expression of an opinion.

There are 5 elements : -Subject matter,against which assurance is required by the intended users -Gathering of sufficient appropriate evidence -Subject matter -A three party relationship involving practical auditor, a responsible part and intended users -Expression of an opinion