[Baertram]

Sure:

Everything defined local can only be used within the area you deifned it
e.g.

if ... then
local var ...
end

var is only known inside the if!

Same for

for ... do
local var
end

loops.

Same for functions

function thisIsAGlobalFuncKnwonInEveryOtherAddonAndAllYourFiles(param1)
end
 
local function thisIsALocallFuncKnwonOnlyIntheAreaWhereItIsDefined(param1)
--e.g. inside a file or even inside an if .. then end, or for .. do end
end

https://www.lua.org/pil/4.2.html