Is number after DateTime2 is for nanosecond purpose?

Question

I have read the document already but i do not fully understand The default precision is datetime2(7) is 7 represent the precision of nanosecond?

Answer 1

No, the number represents the number of digits preserved after the decimal point for the seconds. 3 would be millisecond, 6 microsecond and 7 equivalent to a precision of 100 nanoseconds.