What I think of the word mechanics. The ability of the player to easily utilize the champions kits and knowing the strength and weakness knowing the items viability and its effects to the champion knowing when to play passive or aggressive with the champion.
What you are describing is not only mechanics, but also game knowledge.
Mechanics are the mechanical skills you need to do something: a lee sin ward-jump + ult + q is a mechanic. Another example is kiting, not everyone is good at kiting since not everyone has the need to practice it (I'm bad at it since the champs I play can't kite) so they lack the mechanical skills to do it, we all know how it works but not everyone can do it. Game knowledge is mostly how good you are at reading the game: Knowing when to engage with a malphite's ult is game knowledge, anyone can press the r and hit 2-3 people but not everyone knows whent the right time to pull it off is. Another example might be knowing when to use a CC: we can all stack cc on someone, but knowing when it's the right time and the best way to chain them it's game knowledge.
Items, champion strenght and weanesses and match ups are all game knowledge.
