Just wondering How this works im kinda confused with it. Is it that If the ohms is lower in the cabinet than what you got your amp set to it explodes or something?

Or if the ohms in the cabinet is higher than the ohms youve got your head set at it works ok? damn im confuzzed just at that. Just to clear it up someone explain. thanks.
Impedence is complex, but the easiest way to think of it is the internal electronic resistence of a piece of circuitry.

Just match your Ohms. Differences in output impedence to input impedence can cause gear to not work properly or fry. So just keep them all even and you'll be right.
Okie But i have a jcm cab (bass cab but uses same speakers as lead.) and it says on the plate at the back 16 ohms cab. BUT inside looking at the speakers it says 15 ohms on each one :/ Should i be worried?
Hmm, what you should be concerned about is the overall impedence of the cab. When a whole bunch of speakers are wired in parallel (like in a cab) the overall impedence is a lot less than the sum of each speaker.

As long as the output impedence of your head is the same as the input impedence (16 ohms in your case) you won't have a problem. The speakers are just rated individually for upgrades/replacements/modifications.