.chk files and switching the swap file

I was going over TechRepublics Ultimate Preventive Maintenance Checklist (Very cool) and came across something I didn’t quite understand. I would just like to find a link to an article or something that can explain in more detail the purpose of .chk files, what switching the swap file means and why it is good to do it. (Computer enthusiast and recent beginner!)

Thanks
sherry_stuart@hotmail.com