The result variable is a special variable that serves as an implicit return variable, which exists because the control flow semantics of the return statement are rarely needed. The result variable is initialized in the standard way, as if it was declared with var result: ReturnType. For example, the getAlphabet() function could be rewritten more concisely as

proc getAlphabet(): string =
  result = ""
  for letter in 'a'..'z':

A possible gotcha is declaring a new variable called result and expecting it to have the same semantics.

proc unexpected(): int =
  var result = 5
  result += 5

echo unexpected()  # Prints 0, not 10