There's a process you might notice in the CPU tab called 'kernel_task' that could be taking a large share of resources. Don't panic and don't shut it down! The process simply ensures your CPU isn't working too hard by forcing other memory-intensive Mac processes out. As a result, it might seem like one of the heaviest processes on the list. Similarly, 'mds' and 'mdworker' help index files for the Spotlight search, which sometimes spikes their appetite.