No. echo() will print out strings in the toribash window. it was just an example. If you want to store "foo" into Variable just write

Variable = "foo"

into the text file. If you put

dofile("yourTextFile.txt")

into your script file, "foo" will be stored into Variable.

This:

out = io.open("yourTextFile.txt", "w")
out:write("Variable = \"bar\"")

will store the Variable but remember that all other values will be lost. You could use

out = io.open("yourTextFile.txt", "a")
out:write("Variable = \"bar\"")

to "overwrite" the value. In fact it will just put ' Variable = "bar" ' at the end of the file, leaving all other data. After a while you will have a monster text file though.

btw: Usually variables start with small letters. It's not necessary but it makes it easier to read the code.