What is the difference between chronic leukemia and acute leukemia?

Nature. Acute means urgent require treatment right away. Chronic likely present fora while and may not require treatment urgently.
Aggressiveness. Acute leukemias often present faster with an aggressive course and require urgent treatment. Chronic leukemias have a slow moving course and over years can progress to an aggressive phase. Treatments for acute leukemias thus require more complex chemotherapy and often bone marrow transplant.