alekhine opening
Not necessarily. Hypermodern theory is all about controlling the center with pieces rather than pawns. Nowhere does it state that White's pawns are a "weakness"; it just challenges those pawns in a different way.
To the original poster, do a simple google search on "hypermodern" "openings" to learn the principles behind Alekhine's Defense.
this is the standard alekhine opening: it seems to me that black has not only given up tempo but left white with some great chances to develop completly in the center. im sure there is a point to this, otherwise it wouldnt be as famous as it is. could someone please explain the opening to me?
The diagram you included does not show the standard Alekhine defense, where there are other variations. It shows the two opening moves that are the very definition of Alekhine's defense. It is named for the 4th world champion Alexander Alekhine, who first brought serious attention to the opening when he played it in Budapest in 1921. This is the standard continuation:
At this point, the most common moves are 4.Nf3 (the Modern) and 4.c4, which gives rise to a number of variations.
The answer to your second question "Why does black let white set up a pawn center?" has already been answered; The opening is of the hypermodern school of chess thought.
The answer to your first question "Why does black spend so many tempi just to bring his knight to d5 or b6?" is more complicated. The argument is that black has 'lured' white's pawns into becoming overextended, and so will have an easier time exploiting their weaknesses. Most Grandmasters do not believe that this is worth the tempi spent, so it is generally not seen as more than an occasional weapon. I agree with this sentiment, and think that it is much more worth the time to develop multiple pieces and gain a foothold on a wing before challenging white's center. The Indian defenses (1.d4 Nf6) tend to follow this pattern. However, the defense is very playable at club level and, if you would like a surprise opening in which you could specialize, this defense would work just fine.
My vague understanding is that you tempt the pawns to become overextended so you can go around them. You can also win a psycological advantage by using an opening that your opponent may feel uncomfortable with.
Down at our level, it gives a good game and as black I don't seem to have trouble equalizing. Be creative. Have fun.
The Alekhine allows White to get a large and extended center to try to attack it later. Although the Alekhine is not so popular in the GM level, it is still an opening that requires preparation to play against.
Pawns cant move backwards.
Irish GM Alexander Baburin plays the Alekhine often, hes pretty good too only finishing 2nd behind GM Peter Svidler in a tournament last weekend.
this is the standard alekhine opening:
it seems to me that black has not only given up tempo but left white with some great chances to develop completly in the center. im sure there is a point to this, otherwise it wouldnt be as famous as it is. could someone please explain the opening to me?