What does it mean to compute the autocorrelation between two different time istances in a time series? I don't well understand the concept, which is the sense of measuring between two time istances of the same series? Thanks!
auto-correlation is computed on the n pairs of values k periods apart . For example if we have 60 observations we can compute the auto-correlation of lag 1 using 59 pairs. likewise we can use 48 pairs to compute the relationship between values 12 period apart.
autocorrelation is an ensemble measure based upon a number of relationships for a particular lag (temporal distance)