How many points are won/lost during this exchange?
First of all, moves 2 and 4 absolutely cannot be swapped for the same result. If white plays at 4 first, black would connect at 2. And white has to spend another move protecting the cut. It's a whole world of difference.

Secondly, the name for white 2 is "throw-in". The corresponding Chinese name is "扑", which means "to leap".

Now, let's analyze the situation: 

$$ six=two
$$ -.......
$$ -....... 
$$ -...OOOO
$$ -4....XO
$$ -1OOOOOX
$$ -XOXXO.X
$$ -2X5.XX.
$$ -3......
$$ --------


versus

$$ Optimal exchange
$$ -.......
$$ -....... 
$$ -...OOOO
$$ -c....XO
$$ -2OOOOOX
$$ -XOXXO.X
$$ -1Xa.XX.
$$ -b......
$$ --------


In the actual game, black presumably captures two stones (2 and 6) while white also captures two stones, so that part balances out. Compared to the optimal solution (lower figure), black put 2 more stones in his own territory (at a and b in the lower figure) while white only put one more (c). So that's a -1 point for black right there.

The true loss for black lies in the fact that black could have had sente (lower figure), instead of gote as happened in the actual game. The point value of that is dependent on the rest of the board, but is usually quite high.