Using a set of conditions you can specify that under certain circumstances the system can use special pricing. This can be that a specific agent or group shall use different rate, or worklogs connected to a specific ticket type shall be different charged, handle of a specific type of assets, etc.
The rules can be set up to check property conditions on Ticket (the ticket the current worklog is created from), CI attached to the ticket and the already existing worklogs connected to the ticket.
Charging Rules are connected to the Charging Plan.