In Google Sheets, ERF is a function that returns the error function, also known as the Gauss error function, which is used to calculate the probability of an event occurring within a certain range of values in a normal distribution.

The function requires at least one argument, which is the lower bound of the range, and an optional second argument for the upper bound. The output is a decimal value between -1 and 1, where a negative value represents the probability of the event occurring below the lower bound, and a positive value represents the probability of the event occurring between the bounds.

The syntax for using ERF in Google Sheets is:

=ERF(lowerbound, [upperbound])

Where "lowerbound" is the lower limit of the range and "upperbound" is the optional upper limit of the range.