An outcome is a statement about the state of the future. An outcome is the result of things that we do.
A requirement is a statement about something that is done or will be done.
Walking 30 minutes a day is a requirement. Losing 10 pounds is an outcome.
A requirement can always be stated in terms of an activity. An outcome does not contain the activity required to create the outcome.
Goals are a special type of outcome.
It takes time and thought to clearly articulate outcomes and requirements. Often they are intermixed.