Sure, its probably best to explain with an example, see this song file: Dropbox - Phrase 0Sxx demo.xrns - Simplify your life
So you can play a phrase from a specific line by specifying the line number (in Hex) with the 0S command. In this example 0S is being used to play a phrase like its a drum sample. Before phrases you could chop up a drum loop like this but you would need to put each hit on a different track if you wanted to process hits with different eq/compression settings. Then you put them in a group for bus processing. However if afterward you wanted to chop up the programmed break you would have to copy and paste/reprogram each track. I actually made a tool that lets you do what 0Sxx can now do with phrases: New Tool (2.8): Pattern Offset
Now you can do all that by sending different hits to their own fx chains, program the drums in one phrase and then chop that phrase up in the pattern track. So its more convenient if you want to chop up drum breaks and so on. Hope that makes sense, its probably easier to understand by looking at the attached song.
There are of course other ways in which you can achieve the same effect but I’m still figuring all this out.