What is a Resolution time?
Resolution time is the time in which a ticket gets resolved. It starts the second when a ticket comes into your helpdesk and ends when your agent or the customer hit the Resolve button. Sometimes, tickets gets resolved automatically by a Rule running on the background.
The most typical situation when a ticket gets resolved automatically is when a customer writes in about a question, customer support agent replies to the ticket and the customer never replies back. Usually a rule is triggered after a couple days of inactivity which in this scenario will resolve a ticket.