When would we need a javascript client template engine?
The reason for a jQuery template engine is this:  developers write Javascript code to create new chunks of HTML to inject into the page.  This usually is done by concatenating many strings with variables for values, and it becomes difficult to maintain.
With a jQuery template engine, the process of creating HTML at the client can benefit from all the same advantages that server-side developers now have with their templating engines.
Recently, I found out that jQuery has an official template engine which was contributed by the Microsoft team.
Also I had heard about jTemplate from my friends, but I'm still confused: 

When & where might I need to use these plugins?
How should I choose between the many client side template engines?