Don't cut it!!!!
Those small plantlets are called keikies, which means baby. Once it has several roots between 2-3" long, it can be removed from the mother plant.
Just use the back edge of a butter knife as a wedge between the bigger cane and the baby. With just the right pressure, it should pop right off.
It is from a Dendrobium phalaenopsis orchid. You can pot it up using the proper sized pot and the appropriate media. Quite probably a three inch clay pot would work nicely.
