These are a bit on the basic side but I bet everyone finds 1 or 2 things in this list they didn't know:
Towers deal physical damage so only armour offers increased protection from their shots.
Minions push slightly harder and take less damage when their enemy towers are destroyed in that Lane. The more towers are down, the harder they push.
Killing only the caster (ranged) minions in a wave, leaving the melee ones alive, sets that wave up for a big counter push in a few minutes' time, without anyone even being there.
Junglers can smite while stunned/rooted etc but NOT when suppressed. Suppression cannot be removed by summoner spell Cleanse, but it can by using a Quicksilver Sash.
Lethality is essentially flat armour penetration per champion level. As the lethality owner levels up, they negate more armour from their target.
Everyone benefits from the armour shred on Black Cleaver. Use it to enhance your AD allies' damage on an ene...
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