In database management, isolation levels are a critical aspect that impacts how concurrent transactions interact with each other. They determine the visibility of changes made by one transaction to other concurrent transactions and help control phenomena like dirty reads, non-repeatable reads, and phantom reads. The main SQL isolation levels defined by the SQL standard include Serializable, Read Committed, Read Uncommitted, and Repeatable Read. Each level offers a trade-off between consistency and performance, with higher isolation levels providing greater consistency at the cost of potential performance degradation due to locking and blocking.