Polly Circuit Breakers are used to handle transient faults and longer outages in .NET Web service consumers. They can be viewed as state machines that start in a closed state, allowing the flow of requests across it, but move to an open state when a problem is detected, blocking all requests for a specified period. The circuit breaker then moves to a half-open state where the first request is treated as a test request, and if successful, the circuit closes and normal operation resumes. Polly offers two variations of the policy: basic and advanced, with the basic one cutting the connection when a specified number of consecutive failures occur, and the advanced one cutting the connection when a specified percentage of errors occur over a specified period and when a minimum number of requests have occurred in that period. The circuit breaker can be used to handle connections to multiple endpoints, sharing state while executing requests.