The function of a cache in computing is to temporarily store frequently accessed data to speed up data retrieval processes. Caches reduce the time it takes for applications to access data by keeping copies of data closer to the processor or user. When a requested item is found in the cache, it can be delivered much faster than retrieving it from the original storage location. This improvement enhances application performance and responsiveness, particularly in high-demand environments, and is crucial for optimizing resource utilization.