These options define what it means for two files to be duplicates of each other. You may consider two files to be duplicates if they have the same name. Another person, whose needs are different than yours, may consider two files to be the same if they have the same content, regardless of their names. It really depends on the situation and what you are using this tool for. Choose any combination of the following options:
Names Match
Sizes Match
Create Date/Times Match
Last Modified Date/Times Match
Contents Match
File Timestamps can be a little unreliable to use as duplicate criteria due to the way that the different versions of Windows handle timestamps. Two files can be identical yet have differing dates. Don't put too much stock in differing timestamps.
You are required to select either the Names Match or the Sizes Match criteria as an initial selection. You can then add any of the other criteria.