Definition of connectors
At poker, the connectors are cards that follow each other. 2-3, 3-4, 6-7 are connectors. There are two types of connectors; the matching connectors (e.g. 5-6 hearts or 5-6 spades, etc.) and the unmatched connectors (5 spades, 6 hearts). The matched connectors have on average an additional 5% equity over the connectors unmatched ones, which is not negligible.
The playability of the connectors
The connectors, especially the assorted connectors, are very popular as a starting hand for poker players. One of their greatest strengths is their playability. Even though a hand like A2 has a higher absolute value than a hand like 9-10 at the heart, a hand like 9-10 at the heart will have better playability. When a hand has more playability, it will be more winning in the long run. If you have initiative and a matching connector, there are few flops you won't bet on. The connectors matching ones give us good reason to bet. For example, if with flop 9-10 in the heart you see a flop as 7-8-2 with only one heart. You will bet in position with your draw. Your opponent might fold to give you the pot. But even if he calls, a 2nd heart on the turn will give you another good reason to bet. You are betting here to maximize your fold and because your hand just won in equity.