In the casino game of blackjack, early surrender is the same as late surrender with one important difference: In early surrender, you have the opportunity to surrender BEFORE the dealer checks to see if he has a natural blackjack.  Even if the dealer does indeed have a natural, if you surrendered before he checked, you retain half your bet.  This differs from late surrender in that your bet would be lost if the dealer pulled a natural, and then on any other hand you may surrender for half your wager.

As you might surmise, early surrender is a TERRIFIC rule for the player.  That's why, unfortunately, you almost never see it allowed in a casino.   In fact, even being a pretty avid blackjack player, I had never so much as heard of early surrender--much less actually seen it offered--before reading a blackjack FAQ detailed almost to the point of obscurity.  

While you might not think that early surrender isn't much different from late surrender, saving yourself from an automatic loss when the dealer has a natural is invaluable.  Numbers don't lie:

Playing with traditional Las Vegas strip rules and six decks, , the house's advantage is 0.5437%.  If you allow late surrender, the house's edge drops nominally to 0.4744%. Allowing early surrender, however, lowers the house's edge to negative 0.0801%--the player actually has a slight advantage!1  In fact, the only way under Vegas strip rules for the house to regain the advantage while still allowing early surrender would be to play with upwards of 50 decks (more decks is always worse for the player).  Even playing with the extremely crappy Reno standard rules (no doubling down unless you have 10 or 11!  ugh!), allowing early surrender with six decks drops the house's edge from an astounding 0.9404% to a much more reasonable 0.2307%.

I reiterate, this is why you never see early surrender offered.  Late surrender is rare enough as it is.  If you find a table somewhere offering early surrender, I suggest you take advantage of it before the casino manager gets off the crack and realizes how retarded he is for allowing it.  And, please, tell me where that table is!

1This, incidentally, is why most books on blackjack that claim to "Put the odds in YOUR favor!" are such a scam--sure, the odds could be in your favor if the house was actually offering early surrender, but none do2 so it's a moot point.

2The house always wins.  ALWAYS.