An open-ended straight draw refers to a hand where a player is one card away from completing a straight and has four consecutive cards that allow for two different ranks of cards to complete the straight.
Having an open-ended straight draw provides eight outs (four cards of each rank) to complete the straight, offering a reasonable chance of hitting a straight with the next card dealt.
It's the opposite of an gutshot straight draws where one card can complete the straight. Open-ended straight draw are by definition, more favorable than gutshot draws.
A player holds 2♥2♥ and the board displays 2♥2♥2♥.
Drawing either a 5 or a 10 on the next card would give the player a straight.