The Chain tag means the Strike jumps from one target to another, it can bounce to a number of additional targets as the Chain number, with each bounce being a separate Strike (that does not trigger the Chain tag).
Each bounce does one dice less damage, at no dice, the next bounces do no damage.
A Ranged Strike bounces to another target as if the previous target shot it.
A Melee Strike bounces to another target in your range.