What are the key differences between distributed computing and parallel computing, and how do these differences impact their respective performance and scalability?

Distributed computing involves multiple computers working together on a task, often across a network, while parallel computing uses multiple processors within a single computer to work on a task simultaneously. Distributed computing can be more flexible and scalable but may face challenges with communication and coordination between the computers. Parallel computing can be faster and more efficient for certain tasks but may be limited by the number of processors available. The choice between distributed and parallel computing depends on the specific requirements of the task at hand.