If you play Magic: The Gathering, but did not start back when magic began, there are a few abilities that creatures have that may seem strange to you. If you Have recently bought a lot of old magic cards, which can be one of the most fun and rewarding things a new player can do, you may get some cards that seem useless since they have a high mana cost to play them, however, sometimes these cards can be game changers.
You may not know how to use these abilities that old Magic: The Gathering creatures have, but flanking is one of those abilities that can be deceptively powerful. The basics of flanking are, when a creature without flanking is assigned to block the creature with flanking, it gets minus one to its power and toughness. This means if you have a creature with one power and one toughness and flanking and it is blocked by a creature with one power and two toughness, the creature that is blocking will become a creature with zero power and one toughness, causing that creature to die when hit by your creature, but your creature will not die since the creature it is fighting does not have a high enough power anymore.
This may seem like a decent ability, but you will usually notice that these cards have a high mana cost for their power and toughness. This may lead you to put them away and forget about them, but you can use them as a secret weapon.
If you use a deck with creatures that have flanking you can use spells that force your opponent to block the creature. Spells that give your creature provoke, which forces a opponents creature of your choice to block said creature, or a luring spell which forces all creatures controlled by opponents to block your creature, you will find that all creatures blocking yours with one toughness will die before combat damage is assigned, also all creatures with one power will not do combat damage. Since all their creatures are blocking your one with flanking, the rest of your creatures can hit the opposing player freely, which greatly increases their effectiveness.
This can be a board changer, if your opponent uses spells that replicate one power one toughness tokens, as it will destroy all of their tokens, leaving their side bare, and ready to be attacked by you at will.