I think everyday tasks isn't that hard to define. It's pretty much everything you do in your personal digital life these days:
Internet, email, social networking, listening to music, watching movies and series, basic content creation work (text, photo editing and management, light video editing for some people). It can also include varying degrees of spillover from your work life, managing personal finances, updating a website or blog. Probably also includes some gaming as well for some people. But since everybody knows that serious gamers are very picky about hardware for a "real" gaming rig, I doubt there's any confusion on their part between an "everyday tasks" machine and a "gaming" one.
Basically, anything which requires specialised software that people don't tend to use unless they work in a specific industry I would say is the "not everyday task" category. There's obviously some overlap - a high school kid might use FCPx to cut skating vids just because it's the software at hand. But there's a different kind of user as well who uses the same software at a more demanding level, and they tend to be pretty up to speed on what they want and need in a work machine. Again, there's not likely to be much confusion as to where this kind of user would draw the line between things to do on an "everyday tasks" machine and things you just need to do on your work rig.