Naked pairs and triples
Use pencil marks to clear candidates when two cells share the same two options.
Turn on Notes and write the possible numbers in each empty cell. If two cells in the same row, column or box both have exactly the same two candidates, for example 3 and 8, then those two numbers must go in those two cells. No other cell in that group can be 3 or 8, so you can erase them there.
A naked triple is the same idea with three cells that share three candidates between them (each cell may show only two of the three). Hard puzzles on LogicBright are built so that pairs, triples and pointing are needed.
Tip: after you erase candidates, look again for singles. Clearing a pair often reveals a hidden single right away.
Practise it
The Hint button on every puzzle explains the next step in the same plain language, so you can learn as you play. Play a Killer Sudoku puzzle.