DevOps practitioners can enhance their CI/CD workflows by leveraging concurrency and parallelism within CircleCI to reduce build times. Concurrency refers to the execution of multiple tasks simultaneously, and CircleCI's free plan supports up to 30 concurrent tasks. Parallelism, on the other hand, involves splitting work among identical job copies to optimize task execution, which counts towards the concurrency total. By adjusting the parallelism setting in the CircleCI configuration file, users can efficiently manage their workflow to maximize the number of concurrent tasks. This approach enables quicker job completion, allowing developers to focus on testing and deploying software. Understanding and utilizing these concepts can significantly improve pipeline efficiency, and those seeking further optimization can opt for expert reviews through a premium support plan.