What is "Script Hash" address exactly and how does it work? I found out this address playing with blockchain

https://blockchain.info/address/3NukJ6fYZJ5Kk8bPjycAnruZkE5Q7UW7i8

I found out it's something called "scripthash". How does it work exactly? How does it differ from a normal address?

I found out this - https://en.bitcoin.it/wiki/BIP_0016 - but I still don't get it and I don't get the point. 


  The benefit is allowing a sender to fund any arbitrary transaction, no matter how complicated, using a fixed-length 20-byte hash that is short enough to scan from a QR code or easily copied and pasted.


How does it differ from what is possible today - scanning just the address of the reciever?

edit: And adding one more question - why exactly is this transaction with the mentioned address as input

https://blockchain.info/tx-index/3618498

included in 94 different blocks? How does that even work?
The P2SH, as defined in BIP 16, states that


  The purpose of pay-to-script-hash is to move the responsibility for
  supplying the conditions to redeem a transaction from the sender of
  the funds to the redeemer.
  
  The benefit is allowing a sender to fund
  any arbitrary transaction, no matter how complicated, using a
  fixed-length 20-byte hash that is short enough to scan from a QR code
  or easily copied and pasted.


Hence it allows any client implementation to fund a transaction with an arbitrary script, without the client necessarily having to understand it. You see, there are some quite complicated possibilities for transactions to state their claiming conditions, which may put different implementations of clients under a dilemma: each time a new script type surfaces they'd have to implement it so that the client can send transactions that make use of them.

P2SH has the advantage that the client does not necessarily have to know how to build such a script, it just has to know how (given an arbitrary script, or indeed its hash) building a script that first verifies the script and then uses that script to verify the claim itself works.

Suddenly, if I provide you with a hash of a claiming condition (script) you can send me bitcoins without actually having to know what security mechanisms I put in place to secure that only I can then spend them.

As an added bonus it really keeps the addresses small (25 byte script) which can easily be displayed in a QR code or may even be typed by hand.

The reason transaction 4005d6be is included in so many blocks is all of those blocks are orphaned, so the miners that included them supported a version of P2SH but never got a majority. The fact that this transaction is still unconfirmed is probably due to it being not a true P2SH script.