T5's VHO's (T12's) are florescent bulbs - PC's (power compacts floures, but not as strong as VHO's or T5's (this is hotly depabed though) and halides are the closest thing to real sun you can get (so everyone says).
Each has it's positives and negatives.
Halides - run hot, can be expensive, and suck electricity
T5's T12's - don't run as hot, are less expensive, but can be bulky and long
PC's can be good if used correctly, but are also, mostly to weak for good coral keeping and tent to bloom algea when bulbs re old.
Hope that helps, absent a FAQ for lighting, this is a very complicated question - I recommend you read about lighting for about 6 months to get caught up.
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