ipairs and in pairs?

Not sure, but this is what it says on the wiki:

Ipairs: Returns three values: an iterator function, the table t, and 0, so that the construction will iterate over the pairs (1,t[1]), (2,t[2]), ···, up to the first integer key absent from the table.

Pairs: Returns three values: the next function, the table t, and nil, so that the construction will iterate over all key–value pairs of table t.

Pairs is here.

Ipairs is here.

I hope this helped you!