Bureaucracy is a hierarchical structure that is used by large organizations to implement policies. In other words, it is when you have a boss at the top of the structure and his/her orders are carried out by multiple layers of subordinates. Each level reports to the one above it.
The major advantage is that it allows organizations to grow large. There is no way that you could have a company of any significant size without bureaucracy. The boss would never have a chance of supervising everyone in the company.
The major drawback is that there gets to be more "red tape" as lower level bureaucrats follow rules and procedures even if they are not really the best way of handling things.
Bureaucracy is also meant to allow an organization, governmental or private, to carry on its day to day business through changes in power. This is a tremendous advantage since if all of the people involved with day to day operations were let go when a new administration or CEO came in, it would completely disrupt the operations of the entity. The institutional history and intelligence would be completely lost in a change in power at the top. New people would have to be hired and trained, causing significant down time for any organization, which would be completely impractical. If I need a passport and there is a new president in January, I do not want to wait for new people to be hired and trained in the interim. And that is a fairly trivial example. Image a complete turnover in the Defense Department for each new administration! For the most part, in government and in private industry, a change at the top effectuates not all that many personnel changes, so the bureaucracy can carry on. As much red tape as they seem to generate, we would be even less pleased without them.