Endurance is a measure of your overall physical fitness. A high Endurance gives bonuses to health, environmental resistances, and the Survival and Unarmed skills.

“You can’t keep a good cowboy down, not if he’s the endurin’ type… and not if he’s got a six-shooter the size of all tarnation.”

As the description says, Endurance increases your Health and some resistances. Presumably your resistance to poison is the same as in Fallout 3, as your radiation resistance remains unchanged. Since you only receive five Hit Points per level in New Vegas (as opposed to 10 in Fallout 3) Endurance plays a more crucial role. Most importantly, however, in New Vegas your Endurance determines how many stat-boosting Implants you can receive. There are a total of nine Implants, and you can get one for each point of Endurance you have… not including an extra Endurance you may get from an Implant. If you want as many Implants as possible, you’re going to want a high starting Endurance. Since this attribute also boosts your Survival, it’s a good pick for people playing in Hardcore mode.

The more the merrier in Endurance; start out with a whopping eight Endurance. This will allow you to get all the Implants in the game, save the Charisma Implant.