The s means the two cards have the same suit and two cards in a row mean connectors. In this case, it means 89s, 9Ts, TJs or JQs. If it had just been 89s+ it would mean any suited connectors from 89s to AKs. A9o+ means Ace with a lower card of a different suit. o means offsuit.
The worst poker hand to play and the worst poker hand is a 2-9 offsuit. A 3-9 offsuit is regarded as the worst hand in poker or the worst hand in 5 card poker, while a 4-9 offsuit is also considered the worst hand in poker or the worst hand in 5 card poker.