In my experience, it's been a combination of the following:
- Measures by results/output, rather than input.
- Motivating, inspirational leader that you can respect and look up to.
- Sensitive to team members' needs - support/training/career, etc.
- Quickly resolves conflict, diffuses difficult situations.
- Understands your job - they may be able to actually do your job, but hired you to do that.
- Handles/filters-out the stuff thats' not important or impairs the teams' productivity.