Scopes

Scopes are what define the range of functionality to a variable or function. This specifically applies in Lua to local variables & functions. When you define a variable or function with local, its scope is defined by the innermost block of code you define it in.
Example of various scopes:
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local x = 15 -- scope is script-wide, x can be accessed anywhere inside of this script
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​
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function a()
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    local first = true -- first can only be accessed throughout a()'s code block
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    if first then
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        local second = 123 -- can only be accessed within this if statement
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        print(second) -- Output: 123
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    end
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    print(second) -- nil, cannot access that variable anymore
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    print(first) -- Ouput: true | we can access this variable since we're still inside of the function's code block
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end
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Another example showing a function's scope:
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local function outputTable(t)
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    local function output(t)
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        for k, v in pairs(t) do
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            print(k, v)
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        end
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    end
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    output(t) -- output function is only accessible inside of outputTable
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end
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​
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outputTable({1, 2, 3}) -- works, outputTable's scope is script-wide
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output({1, 2, 3}) -- will return an error, output is inaccessible since it's not inside the current scope, it is inside of outputTable. 
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Closures

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