what is the open transaction ?

I read the document about the sysprocess table on MSDN.


And I get this line
open_tran | Number of open transactions for the process.

But I don't know what's open transaction, I can't get the defination of it from the web(MSDN or Wiki etc).

So anyone can explain it and why I can't get the defination on the web?

TNX A LOT FOR YOUR REPLY

Origami