Interference in chess happens when a piece is sacrificially placed between an attacked piece and its defender, interrupting their line of communication. This tactic is infrequent and can be easily missed. It is a rare opportunity because the piece being defended must be worth more than the sacrificed piece, and the interposition must pose a threat as well. It can be characterized as a strategy that involves obstructing attack lines with blocking moves, which can also include moves that disrupt defensive lines, expanding the definition.
Have a look at the following game that demonstrates a typical interference:
Nice, huh? But that’s not all. An instance of interference that is more nuanced arises when a piece obstructs two lines at the same time. In such a scenario, the piece in motion need not be a direct threat on its own. Its presence causes the adversary to stumble as they attempt to capture the piece, as doing so will inevitably result in breaking one of their defensive lines.
Check the following diagram: