Waste toners are discarded toners from the opc (organic photo conductor) unit.
When you print, not all of the toner goes on the page. There will be some left on the drum surface. The excess toner is typically called "waste toner". The drum's cleaner blade wipes out these toners and discards it to a waste receptacle/container.
Waste toner containers can either be emptied or replaced.
Usually,the container deteriorates after 5 to 6 emptyings, and so, you will need to have it replaced with a new one.
A Detailed procedure in replacing a waste toner container for Phaser 6110 MFP can be accessed using this link: