2-way coaxials have a separate midbass driver with a tweeter mounted on top of them. 4-ways are pretty much a gimmick, the extra '2-ways' coming from something like a super-tweeter and midrange, or something similar, which do little to improve the sound.
In general, there are better 2-ways available than there are 3-, 4- or 5-ways, but there are always exceptions to the rule.
