An inside straight draw is a draw to a straight that's missing one of the cards in the middle (as opposed to on the end). 4578 is an inside straight, 4567 is an outside straight. Also called a one-gapper or a gutshot.
Four cards that with another card of a specific face value or rank, and only that one rank, would make a straight. For example, consider this hand 3s, 7c, 8h, 9c, Js. If you hold the 7, 8, 9, and J and discard the 3 you are holding four to an inside straight. You must get a card with a face value of 10 to make the straight. Now consider this hand 3s, 7c, 8h, 9c, 10h. In this case if you discard the 3 you are not drawing to an inside straight because a card with a face-value of either 6 or J will make the straight. Obviously you have a better chance of making the straight in the latter example.
"Inside Straight" is a poker term that connotes the circumstance when a player has 4 of 5 cards needed for a Straight Flush, missing only a card inside the sequence rather than at either end, and gets that missing card for a win. As an example, let us say that a certain online poker player is holding card faces with a 3, 4, 5, and 7, and needs a 6 to complete the Straight Flush. Getting that needed 6 is "making the inside straight."
A series of cards that can make a straight if you are dealt a specific middle card to complete it. (e.g. A2356 - you will need a 4 to complete the hand. The 4 is the 'inside straight' drawing card necessary to accomplish this hand.)
Situation where you are drawing to or have made a Straight where the card you needed (or received) was a middle card that completed the Straight. An Inside Straight is harder to draw than an Open Ended Straight which is discussed below.
drawing to an inside straight is drawing to a straight that is missing a card in the middle eg. drawing a card on a 2356 looking for a 4. An outside straight would inlcude 4 consecuvite cards 3456 to improve your hand you would have to draw a 2 or 7
Four cards to a straight where the one card you need to complete the straight is in the middle of the run. For instance, with a 4c, 5h, 7d, 8c you would need a six of any suit to complete the straight. Also called a gut shot or belly buster.