Well, you must have heard about OLTP-Online TRnasaction Processing. That is when you do e-commerce activity on net that is through WEb application(web site), you need to consider various transaction principles generally described as ACID-Atomic/Consistent/Integrated/Durable
So you have to determine if transction activity is success or failure. Consider withdrawing of a check in the bank. There you submit the check to the counter after entering initial details, it goes through different vaification stages.If any of the step is not successful in varification, the entire transaction is called a failure and you will not get Money ! So if you automate this process through web, MTS will help you determine if the process is successful or a failure. By the way transaction controllers like CICS and Tuxedo are there for years.(Before the inception of www)
2. What is MTS relation with respect to .NET or what role does it plays?
Well MTS is heavily dependent on COM components.In fact sometimes we call it as COMponent manager only.Whole transaction is controlled by components called as COM. Now role of COM in .NET is another big issue.Check out FAQ written by me on COM/DCOM forum. FAQ195-1734