A busser, occasionally called a bus boy but more commonly called everything else (words I won't care to write), is a key part of a restaurant. As every establishment is different, different people may perform the functions of a busser. Sometimes the host/hostess bus tables, sometimes it's the server's responsibility, sometimes managers help out, and sometimes they hire specific people to take care of cleaning up tables.
It's the busser's job to clear tables and reset them for the next round of guests. Other common requirements of being a busser include: checking salt and pepper levels, filling sugar caddy, cleaning up spills, maintaining the restroom, and general work. Sometimes bussers are responsible for doing dishes.
As a busser you should expect minimum wage, but oftentimes the servers are required to tip you out 1 or 2 % of their total sales. Depending on how busy the restaurant is a busser can make a fair amount of money for doing unskilled labor.
In the front-of-house, a busser can be promoted or cross trained to host or serve. Depending on their age, they could be a bar back. In the kitchen bussers can become dishwashers, prep cooks, or line cooks, but they will probably start at a slow station of the kitchen, pantry/salad.