Wow. So you may or may not already know that I play Yu-Gi-Oh!. If you don't, I play Yu-Gi-Oh! I've been a fan of the card game ever since it came out, and the anime is a fun guilty pleasure. People who play the game will probably appreciate this story more, but I'll try to explain it the best that I can for the benefit of anyone who doesn't know how it works:
I just dueled against a guy on DevPro (a tool for playing Yu-Gi-Oh! online) who had no understanding of how the Chain works. To put it simply, the Chain is when multiple effects are activated in sequence, in response to one another. Similar to the Stack in Magic: The Gathering, when effects are no longer being added to the Chain, all of the effects resolve, in reverse order (i.e., the last effect activated is the first to resolve). To put it another way, in programming terms, it's "Last in, first out." Anyway, I had an opponent who didn't seem to get this. Here's what happened:
I had Necrovalley in my hand and a Fiendish Chain set, while he had a Spell/Trap card set. He summoned Evolzar Laggia, and I activated Fiendish Chain on it, to negate its effect. Evolzar Laggia can detach both of its Xyz Materials to negate a summon or the activation of a Spell/Trap card, so naturally I wanted that effect neutralized so that he couldn't negate the Necrovalley in my hand. I activated Necrovalley (its effect is not important to the story), and in response, he activated his face-down card, which turned out to be Forbidden Lance. Forbidden Lance decreases a monster's Attack Points by 800, but makes it unaffected by other Spell/Trap cards for the rest of the turn. Then he used Evolzar Laggia's effect, attempting to negate Necrovalley. Of course, this failed. Why? Because the Chain looked like this: Necrovalley > Forbidden Lance > Evolzar Laggia. As a result, they resolved in reverse order: Evolzar Laggia > Forbidden Lance > Necrovalley. This meant that Evolzar Laggia's effect resolved BEFORE Forbidden Lance did. As a result, when Evolzar Laggia's effect resolved, Forbidden Lance had not yet made Evolzar Laggia unaffected by Fiendish Chain, thus Evolzar Laggia's effect was still negated by Fiendish Chain. If, on the other hand, my opponent had activated Evolzar Laggia's effect first, and THEN Forbidden Lance, then the Chain would look like this: Necrovalley > Evolzar Laggia > Forbidden Lance, meaning that Forbidden Lance would resolve BEFORE Evolzar Laggia's effect, and Fiendish Chain would not have negated Evolzar Laggia's effect.
In summation, if you want to play Yu-Gi-Oh!, learn how the Chain works before you start making rookie mistakes.