What does a Bitcoin transaction consist of? I gather that 2400 transactions fit into a 1 MB block.
That's 436 bytes per transaction record.
But what's in a transaction record?

Is there a good Powerpoint presentation that describes how Bitcoin transactions work?

Thanks.
Here's an interactive diagram showing the indivdual steps through the diagram:


http://staging.spectrum.ieee.org/static/how-a-bitcoin-transaction-works


A typical transaction (simplified) looks like:

Spend:
   20 BTC from a transaction using address:ABC123 

To:
   10 BTC to address XYZ111
   10 BTC to address JKL222


Here XYZ111 is where you want to send your BTC to and JKL222 is your address for the change.

With transations like this you do not know (reliably) where your BTC are coming from. The next transaction will probably spend from JKL222 as ABC123 is all spent.

This in intentional in the Satoshi client so that it jumbles up the change and the sendee's addresses.