Clone a patch : creates a child solution of the main solution, the purpose is to only add things that needs to be changed and import them in the target. once a patch solution has been created, the main solution becomes immutable and can't be changed until the solution is cloned using 'clone solution'.
Clone solution : creates a new incremented version of the main solution by rolling up all the patches into the new version.
patching is good for short term, but eventually the solution needs to be merged, so if your solution is small and you're sure that nothing else has changed other than what your desired changes are, then, export the complete solution as managed and import it in your target.