Implementation of a timer

Could someone explain to me what this code says

//TimerA0 initialization
TCA0.SINGLE.PER = 999;
TCA0.SINGLE.CMP1 = 999;
TCA0.SINGLE.CTRLA = TCA_SINGLE_CLISEL_DIV16_gc l TCA_SINGLE_ENABLE_bm; // 16 prescaler 1 M
TCA0.SINGLE.INTCTRL = TCA_SINGLE_CMP1_bm;

May I suggest that you consult the datasheet of the microcontroller on your board; I think you're using a Nano Every but might be wrong.

PER might refer to period, CMP1 might rfer to a comparator, CTRLA might refer to a control register and INTCTRL might refer to an interrupt register.

I am using arduino nano every

Datasheet available on the product page of the Nano Every under the Tech Specs tab: https://content.arduino.cc/assets/Nano-Every_processor-48-pin-Data-Sheet-megaAVR-0-series-DS40002016B.pdf

Could you please explain me what these lines basically say ? Because I’m lost at the data sheet. I would really appreacuate it

Basically, they are setting various fields within the register space of Timer Counter Register Type A, Instance 0 to the values required to achieve the desired operation.

To know what's really going on, you have to study Chapter 20 the Full Processor Datasheet.