pairs (t)If t has a metamethod __pairs, calls it with t as argument and returns the first three results from the call.
Otherwise, returns three values: the next function, the table t, and nil, so that the construction
     for k,v in pairs(t) do body end
will iterate over all key–value pairs of table t.
See function next for the caveats of modifying the table during its traversal.

 

ipairs (t)If t has a metamethod __ipairs, calls it with t as argument and returns the first three results from the call.
Otherwise, returns three values: an iterator function, the table t, and 0, so that the construction
     for i,v in ipairs(t) do body end
will iterate over the pairs (1,t[1]), (2,t[2]), ..., up to the first integer key absent from the table.

tb = {"oh", [3] = "god", "my", [5] = "hello", [6] = "world"}

 

for k,v in ipairs(tb) do
     print(k, v)
end

1       oh
2       my
3       god

for k,v in pairs(tb) do
     print(k, v)
end

1       oh
2       my
3       god
6       world
5       hello

for i = 1, #tb do
     if tb[i] then
          print(tb[i])
     else
end