My wife is going to take an online course, and they gave her a list of all the things she needed on her computer. This includes:
Sound Card: Available at any computer store for about $20. (Comes built into a MAC).
But don’t just about all computers made these days have sound cards, even if they’re PC’s? If we can hear all the AOL blather…Welcome! You’ve got mail!, and “Goodbye”, then doesn’t that mean we already have the sound card?
Yes, you have a soundcard, built into the motherboard.
Could also be a PC speaker, but I doubt any wave forms are being played through that thing!
Are you plugging a speaker jack into the computer? If so, you have a soundcard.
Just what I thought. Thanks!
The things I don’t know, after programming for 18 years…(but not on PCs).
Yes. And you’re quite right, all commercial PC’s sold nowadays have soundcards – at least all the ones I’ve seen. Theoretically, you could build a PC from scratch and leave out the sound card but most motherboards anymore have them built in anyway!
And I see on preview that ParentalAdvisory has beaten me to the punch. Well, phooey. 
My new Dell had a default set up to do exactly that, as it came without a speaker system. It worked, but not exactly quality. It had me quite puzzled at first, as I had this computer without any speakers suddenly making noises.
The references in the OP refer to what used to be standard. PCs did not necessarily have a sound card and could only do simple beeps. Then the standard was for most to have sound cards. Now many, but certainly not all, have a basic sound card embedded on the motherboard.
There’s a good reason for the old-style speaker to still be there. If there’s major problems on boot-up, the computer may not be able to display anything on screen, but will be able to beep a number of times - this is a code which can help diagnose the error.