From Sudopedia, the free Sudoku reference guide

Naked Single

From Sudopedia

The Naked Single is categorized as a solving technique but you can hardly call it a technique. A naked single is that what remains after you have applied your solving techniques, by eliminating other candidates.

A naked single is the last remaining candidate in a cell. Alternative terms are Forced Digit and Sole Candidate.

The easiest way to find naked singles in the grid is using pencilmarks. Cells with a single pencilmark are easy to spot. Without pencilmarks, you need to inspect the peers of the cell and see if there is only a single digit missing in the peers. You need a good short-term memory to do it this way, but many players prefer to solve easy Sudokus without pencilmarks.

Most players do not mention the discovery of singles to other players. When a Sudoku can be solved with singles only, the entire puzzle is not worth a discussion.