Ignoring the sementics, what exactly is the difference?
It's impossible to give a simple answer, since there are a whole range of different things generally called "regulations". About the only common factor is that regulations are not issued by Congress, but by some sort of "executive" body like the FCC, USDA, DOT, etc.
So, in the strictest and least interesting sense regulations are not laws by definition, since they are not passed by the one body capable of passing laws, the Congress. Many regulations are more like "serious recommendations", in the sense that it's the executive's statement of the sort of behavior that they find acceptable, given the current state of the law. If you happened to disagree with the executive's interpretation, you could go to court and show (a somewhat uphill battle. but not impossible) that the agency had exceeded its authority, or had not followed the right procedure in adopting the regulation, or whatever. You are not bound to follow the regulations, but if you don't you may have a long and expensive fight on your hands. Still, agencies do loose these battles sometimes.
Sometimes, though, Congress will say something like "The IRS will now make rules relating to deductions for home expenses," and the IRS will go ahead and make those rules. These are still regulations, but because Congress has straight out said that it wants the IRS to make rules of that sort, they are almost like laws. I.e. there's very little chance (although still some chance) that a court would step in and invalidate the regulation.