WoW:API ipairs

Native Lua statement:

Used in loop constructs to iterate through the values of a table where the index are only numbers, or where there is no index (an array).

Example:

local fruits={"apple","orange","banana","kiwi"}

for index,value in ipairs(fruits) do 
  DEFAULT_CHAT_FRAME:AddMessage(tostring(index).." : "..value)
end

Result:

 1 : apple
 2 : orange
 3 : banana
 4 : kiwi

would be output to the chat window.