Instructions that you give to your computer. You have to speak its language, and do it in just the right way.
The instructions embedded into a database or computer program that result in an operation being performed. For example, the options for "enter", "search" and "print" are computer commands.
These are the instructions sent to the payload. For example, an experiment may not be started on the ground (or while the balloon is rising) so instructions would be sent to the payload after the balloon achieves float altitude to start the instruments.