After you create a segment, you may want to iterate on it down the line without changing the conditions of the original segment. You can do this by cloning your original segment. You can then add or change conditions depending on what you would like to do with the new segment.
For example, if you have a segment of recent purchasers and you'd like to create a related segment of recent purchasers who also made at least two purchases in that period, using the Clone Segment option will save you from having to set up the same conditions for recent purchasers again.
How to Clone a Segment
You can find the similar segment option by selecting an existing segment and clicking Manage Segment > Clone Segment.
Then, you will be brought to your duplicate segment's definition menu, where you can add or delete conditions. Make sure you give your duplicate segment a unique name to avoid confusing it with the original.