While in theory they should work on Bell's 3G (HSPA) network, I've heard reports that some phones like these don't work on Bell for some reason (various BLU phones are a prime example). I can't explain why there are compatibility issues, but it can happen.
That said, you're taking a big gamble with these devices. Don't expect a quality device by any means, and good luck if anything goes wrong! These phones are cheap for a very good reason... Poor displays, slow performance (don't trust benchmarks shown on the site), and questionable specs (2GB RAM / device shows 3GB) are just some of the red flags.
Look at something like the Moto E if you want a fairly good budget Android phone. Even though the screen is smaller, it's almost a guarantee that it would provide a much better (and more reliable) experience.
As for the whole 3G vs 4G stuff, in simplest terms, consider HSPA = 3G, and LTE = 4G. It's not entirely accurate, but for the sake of differentiating these network types, it makes the most sense for this discussion.