STMicroelectronics RHFL4913S50-03V

The operating temperature is the range of ambient temperature within which a power supply, or any other electrical equipment, operate in. This ranges from a minimum operating temperature, to a peak or maximum operating temperature, outside which, the power supply may fail.

a count of all of the component leads (or pins)

The rated output current is the maximum load current that a power supply can provide at a specified ambient temperature. A power supply can never provide more current that it's rated output current unless there is a fault, such as short circuit at the load.

Line regulation is the ability of a power supply to maintain a constant output voltage despite changes to the input voltage, with the output current drawn from the power supply remaining constant.

Load regulation is the capability to maintain a constant voltage (or current) level on the output channel of a power supply despite changes in the supply's load (such as a change in resistance value connected across the supply output).