Some questions about these topics:

What is MST? What does it mean? How does Loop use MST? 

MST stands for “Magnetic Secure Transmission” - it is LoopPay's patented technology, able to accomplish what EMV, NFC and others have not been able to accomplish in the past few years. It allows a contactless or over-the-air transaction at over 90% of POS (Point of Sale) terminals. (And that percentage is growing as LoopPay refines the technology.) What it means is that merchants don’t have to change or upgrade their POS terminals.  

Technically, MST consists of a coil and amplifier that produces a magnetic signal transmitted from a LoopPay device. The signal is received by the magnetic stripe head inside the POS terminals emulating the swipe of a standard magnetic stripe card.  

Does the POS terminal always pick up the signal from the Fob the first time I tap the image of my card, or press the button on the Fob? 

Not necessarily. In most cases it will, but just like swiping your credit card there are variables that may prevent the mag stripe reading terminal from picking up the signal. We recommend you tap the screen image of your card or press the button on the Fob at least 3 times, with a pause between attempts, to make sure the signal is received. Make sure you let the clerk prepare the terminal in between attempts and let them know what card you're using (Discover or MasterCard debit card, etc.)

Pausing between each attempt will give the POS terminal time to recognize and process the signal. 

How will I know when my payment is transmitted?
The terminal will ask you for a signature for a credit card or your PIN for a debit card.  Or the Clerk will smile and say "WOW".