I know what the different channels mean. I assume there's more to speakers than that, if someone could give a basic overview of what I should be looking for concerning speakers, it would be helpful.
What kind of setup are you hoping for? Theater, gaming, basic workstation?
Cool. I'm no pro, but the more we know about what you want the better we can help you pick out the perfect setup.
The gamers I know use headphones. It's easier to communicate in a team setting when your mic isn't picking up everything. That's also the most economical solution. You can get a high end set of headphones for a few hundred dollars (don't know what currency you use).
Depending on how much you want your windows to shake, and how many ports your PC has, and how big your budget it, you could go for 2, 2.1, or 5.1 setups. With a dedicated sound system, you could do even more, but that's... expensive.
Oversimplified, there are three types of speakers or drivers: highs (or tweeters), mids, and lows (or subwoofers). (Edit, your 2 or 5 will typically be a combo of highs and mids while your .1 is the sub. Some cheap speakers will install fake tweeters and attempt to do it all with mids.) As an audio noob, it might be a good idea to look into sets that you know will work well together. Generally, audio power is measured in ohms or watts (they're different, but this is an oversimplification). It's like monitors and contrast ratios, it matters sort of... You want speakers that produce clear sound even at high volumes.
The hard part about speakers is, you really have to hear them. Speakers are made for a variety of audio inputs. Some speakers are "punchy" for pop songs or have an emphasis on highs for classical music. I would recommend visiting some stores and hearing what you like. Then, after you know more what you're looking for, you can better research other kits and brands.
Finally, how you transmit audio from the PC to the speakers can affect the sound quality. Like monitors, don't use a crappy cable with good speakers. Use the appropriately sized cable so you don't damage it. While fact checking myself, I learned from a coax producer that coiling doesn't actually affect the signal as I was taught, so thanks for helping me learn something today!
I'm looking for a 2 channel speaker setup for my bro's pc, I assume a sub can be added later. Smaller speakers are preferred as there's limited space on either side of a 21.5" monitor on the desk.
D'oh I guess that was an unnecessary info dump. (For some reason PCPP wouldn't let me edit this comment?) For a 2/2.1 channel for gaming, you just need to make sure they emit in at least stereo. For immersion purposes, a 2.1 set might be a better start if it's in the budget. It's hard for tiny speakers to reproduce lows, but that doesn't stop manufacturers from trying
For <$100 (depending on shipping) the Logitech Z623 200W 2.1ch Speakers are very well reviewed and certified by THX. I haven't listened to them yet, but they are pretty tempting. They can put out a lot of power, and reviews say they don't distort too badly at high volumes. They use standard 3.5mm cables, so you'll need to make sure they're hooked up properly (easy) but won't waste an HDMI port.
For more than that I still recommend visiting a local store, even if it's just Best Buy, to listen. Even if you don't end up spending that much, it's still a good idea to figure out what you like.
For less, I'd stick with a the best Logitechs you/he can afford. There may be better stuff out there, and others can feel free to offer their recommendations. Logitech isn't high end, but they usually offer a good value and convenience for the price. Keep in mind you'll probably get better sound quality and immersion for your money with headphones, so when you visit a store, try out those too.
Look for something that isn't Razer.