What is Credit index, index series?

A credit index is a standardised credit default swap on an equally weighted basket of reference entities, with one coupon and one maturity; a credit event of a constituent is settled on that constituent’s share of the notional, and the index continues on the others. An index series is one fixed list of constituents, published on a roll date; a new series, with an updated list, is published every six months, and the most recent is the on-the-run series.