I am learning basics of embedded electronics using ATmega328P ("Beyond Arduino", from "Nuts&Volts" magazine). In many names of registers and signals there appears a small letter "n" as in these: XCKn, UDRn, UBRRnL, U2Xn, etc.
In the project that I am following from the article "n" is substituted by "0" as in these: UBRR0L, UCSR0C, UDR0, etc.
I was digging through data sheet for this controller and couldn't find any explanation where is it coming from, what is the meaning of this letter. I guess it is a number but what does it represent? Why "0" in case of this particular project?
Please, help me understand this.