#1 PsList and PsKillI listed these together because I typically use them in that order. The goal here is to see processes on a machine--with PsList, I find the process ID, and then use PsKill to terminate said process.
As you can see here, there are quite a few ways to return information with PSList and the best part is the fact that it works on local and remote machines. PSKill works similarly to PSList except it is used to terminate processes by process ID.
For more details on this and the following tools, see the original blog posts, "Five favorite Sysinternals tools and what they do" (first five tools) and "Learn about some Sysinternals tools that might be flying under the radar" (second five).