Stall Speed & lock up/ non lock up ?

[tbirdsc357]

I'm afraid that I must pleed ignorance when it comes to the issue of torque converters, soooo......can someone please explain why it is good to have a torque converter with a higher stall speed and, I have seen converters with both lock up and non lock up for sale. What is the difference?

Just trying to educate myself before purchasing one.

Thanks.