Larger data sets tend to have duplicate content. You might be copying information form multiple lists or speadsheets and want to remove any duplicate content. In situations like this, removing the duplicates comes in quite handy.
To remove your duplicates, go to the Data tab, and select "Remove Duplicates" (under Tools). A pop-up will appear to confirm which data you want to work with. Select the data set and select "Remove Duplicates" and you're good to go. This will remove duplicates for the data set you selected. For example, if you have a list of names and email addresses, you can remove duplicate email addresses to organize you list. our resulting list will have only unique names without any duplicates.