Needs Reassurance: This is the opposite of a "self-confident" person. In this extreme case, the person will tend to derive their confidence from having others reassure them that they are doing well rather than from having confidence in themself. In other words, the source of their confidence is external versus internal. This type of person may seem timid and shy to others. They aren't the type to be overbearing, because they don't normally have the confidence to aggressively confront others, unless they have a solid group of people constantly reassuring them that they are correct and doing the right thing. If supervising this type of person, it will be important to let them know from time to time that they are doing a good job. The frequency of the reassurance will depend on the individual.
Self Confident: People with an extremely high degree of self confidence don't really need other people to tell them they're right or doing well, they know it. They still enjoy and appreciate hearing it, but they won't cease to function if they don't get a regular dose of encouragement either. Taken to the extreme, they may appear arrogant and assertive, pushing to get things done their way because they are very confident that their way is correct. It often is.