Halp

Diode : 445nm 9mm diode
Output diode : over 3000mW
Output buck driver: 2.4A current
Lens : G2
Power supply : 2x 26650 Li-ion rechargeable battery.
Duty cycle : 5min on/ 1min off.

I read this and got so little ... I am new and I atm just wanna start learning the things a laser user and buyer should know , not a builder or tech ok so diode is like the engine of a car nm means colour and 9 mm means ??? Output of diode is mw = POWAH right ? wtf is buck driver Duty cycle is determined by what factors ? Ill make another thread bout batteries and lenses ty for answers

9mm is the diode size. They also commonly come in 5.6mm and 3.8mm.
The output is rated in Watts or Milliwatts, correct.
A buck driver is a driver that drops the voltage down. A boost driver boosts it up.
Duty cycle is determined by the heatsink mass and the current the diode is set at.

what does diode size change ? why would i use a buck , why wuld i use boost driver ?

Just the phisical size changes. Buck or boost driver is determind by the batteries and diode used.
So with a 445nm diode you would use a single LiPo battery with a boost driver and if you use 2x LiPo cells in series you would use a buck driver.

I will likewise restate the 9mm is the diode size. We need to know this, so we know what size heat sink to use. There are also 5.6mm varieties of the 445nm diode. However, I'm not sure how the two sizes differ in output specs.