Amps available - amps draw ?


Hello.

I am trying to teach myself the basics, but I am confused about ampage.

For instance, say I have a power source that is 12v at 2 amps. I want to power a simple LED circuit that I found on the internet that is designed for a 12v supply but there is no mention of the current. The circuit is a 50 ohm resistor and 3, 3.6v ultra bright white LEDs. The resistor value was calculated for a 25mA current using ohm's law. What is the resistor modifying? The current or the voltage? Will this circuit be usable regardless of the supply ampage? The voltage/current relationship has me confused.

TIA for any insight you may be able to provide.
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