This command allows you to individually view labels which match the search criteria you entered in the Select... dialog box. This command is only accessible if the All Occurrences option in the Select... dialog box is not checked.
Choosing the Select... command when the All Occurrences option is not checked will select only the first label it finds which matches the search criteria you entered, as stated above. The Select Next... command will continue the search from that label, and select the next label it finds that also matches the criteria. This is extremely useful when you are looking for a specific label but are not sure which one it is, because you can cycle through all the labels that match the search criteria and see the entire label for verification.