How to use a variable by using a string?

If you are trying to print what the variable is assigned to it's

print(var1)

But if you want the name of the variable you could put it in a table like this...

local variables = {var1 = "potato"}

And get the name of it like this...

for i,v in pairs(variables) do
    print(i) -- prints var1
end

You can print variables like this:

local var1 = "potato"
print(var1)

potato

You could also combine strings.

local var1 = "potato"
local var2 = var1 .. "E"
print(var2 .. " or " .. var1 .. "?")

potatoE or potato?

it is possible, you were almost there. Print(argument) can also be used to print variables and the outcome of functions. this can be done in the way you would normally call the variable ie. without the quotation marks:

local var1 = "potato"

print(potato)

likewise you could do the following stuff:

local a=10
local b=5

print(a-b)
-- this would be the same as
print(10-5)
-- or
print("5") -- note, the quotation marks are not neccesary here, since it is a number

quotation marks are actually used so that the software "knows": 'ohh, this is not a variable or a function that the user tries to call, but just some random text'

hope this helps!