BGP AS-Path Attribute:
This attribute is used to decide the best-path for a certain prefix.
By default, if a bgp router gets two or more updates for the same prefix, then, it will decide at the best path by simply looking at the AS-path attribute...ie. which of these routes went through the fewest number of AS and whichever route had the lowest number (quantity, not value) of AS-path, that is the best route