COUNTUNIQUE is a function in Google Sheets that counts the number of unique values in a specified range or list of values.

For example, if you have a column of data with duplicate values, and you want to know how many unique values there are, you can use the COUNTUNIQUE function. This function will count only the unique values in the range, and it will ignore any duplicates.

The syntax of the COUNTUNIQUE function is straightforward. You simply specify the range or list of values that you want to count, and the function will return the number of unique values in that range or list.

Here's an example:

Let's say you have a list of fruit in column A, and you want to know how many unique types of fruit there are. You can use the COUNTUNIQUE function like this:

=COUNTUNIQUE(A2:A10)

This function will count the number of unique values in the range A2:A10, which contains the list of fruit. The result will be a single number that represents the number of unique types of fruit in the list.