I'm looking for one of two closely related algorithms. In both, you have a list of elements, of which you have to choose one by some scoring method. In the first variation, the list is infinite and you can't go trough it all, but you can choose any item. In the second, you must choose to accept or reject an item permanently, so if you get to the end, and the last item is a dud, you're stuck with it.
You have no prior knowledge of the range of scores found in the list. As you look at elements of the list, continuously adapt your threshold for acceptance, until you are able to choose an item without having exhausted the list.
For the second variation (finite list), I've seen it in some semi-joking context about dating, where you spend up until age 35 dating people as "samples" and rejecting them all in due time, then past age 35, take the first person who is above the threshold learned from the previous samples.