What is குற்றியலிகரம் ?

I know what is குற்றியலுகரம். உ which comes after a வல்லினம் (stops) which is in the middle or end is குற்றியலுகரம்.I assume that குற்றியலிகரம்is something similar with இ (or isn't, idk) I also know ஃ, குற்றியலுகரம் and குற்றியலிகரம் are சார்பெழுத்துகள் .

I know that this is a really basic question. I hope I don't offend anyone for not knowing this.