Pointing Pairs and Box-Line Reduction
Use the interaction between boxes and lines to eliminate candidates.
Boxes and lines overlap, and that overlap is a quiet source of eliminations.
Pointing pairs
If, inside a box, every possible spot for a digit lies on the same row, then that digit must be in that row within the box. You can remove it from the rest of the row outside the box.
Box-line reduction
The reverse also holds: if in a row every possible spot for a digit lies in one box, remove that digit from the other cells of that box.