Connectors are sequential cards like 87, 54, 32. If they are of the same suit, then they are called suited connectors, otherwise they are unsuited connectors. There are also one-gap connectors like 53 or 86, and two-gap connectors like 52 and 96.
Connectors are strong because it is easy to make straight draws with them. The closer the cards are together, the more possibilities for straight draws exist. This is easy to see if you just list out all the straights with 87 compared to those with 96.
There are 4 with 87:
But just two with 96: