The Daily Scrum is one of the Scrum ceremonies. It is also often called the daily stand-up or just the stand-up.
What is a stand-up?
The idea in holding a daily stand-up is to get the Scrum Team members talking to each other. The stand-up is there to coordinate dependencies, to identify issues and to fascilitate team members helping each other out.
The key to the stand-up is that it is about the development process. It is not a status report nor is it an opportunity to work on the backlog.
Who attends a stand-up?
The stand-up is for Scrum Team members who are fully committed to the sprint. For people who have responsibilities outside the Scrum Team they may listen in to the Daily Scrum, but they should not interupt unless responding to a Scrum Team member.
The stand-up is not a progress meeting. Managers should not attend the stand-up and grill the developers on progress. There is nothing wrong with having a progress/planning meeting, just be clear that it is not the same thing as the stand-up.
A good stand-up
Martin Fowler describes a good Daily Scrum:
"..there is a different feel to a good stand-up that distinguishes it from an empty ritual."
The stand-up should be friendly, supportive and all about making progress with sprint tasks. If it is tense or dull, then it is almost certainly being done incorrectly.
A good indication of a successful stand-up is eye contact. If the team members make eye contact with each other and shift focus as the discussion moves along, then all is well. If the developers all focus on one individual (say the Scrum Master or a manager) then the stand-up is not working as intended.