Shared: The exact same CD effects all abiliites that share that CD. Activating any of the abilities activates the full CD routine for all abilities that share a CD. It's like sharing a popsicle. Something kids might do, but not many game designers. It basically is used to force a player to choose between one of two abilities.
System: Abilities that are on the same system CD cannot be active at the same time. Typically when one of the system abilities is active, all other system abilities go on CD for the duration of the active ability. Once the active ability is no longer active it will go on its normal CD, and the other system abilities become available. This is commonly used.
Global: When any ability is used ALL abilities that are on the Global CD go on a short CD before any of them can be activated again. This CD is always the shortest of the three, typically measured in units as small as half seconds. Some abilites may not be on the Global CD, and thus in games that use a Global (almost all of the majors) Off Global Abilites are very desirable.
STO does not use a Global CD. STO is designed around very fast activation or stacking of abilities. Globals are designed to inhibit this. Thus a Global is not included in STO
There's a reason why industries develop standards. Fighting that is baffling.
This can help you if you make any friends, or post on any other boards, so that people understand you. If you insist on using them incorrectly, I suggest that in person you do so while holding a drink. People may assume you're drunk and not....um....less well informed. If you're posting on the forums....use a lot of LOL! in your posts and leave it at that.