What does T/T mean?

I am interested in an item and want to buy it. I have never bought anything yet so I'm a real novice. They say : T/T (30% deposit,70% before shipment) Can you tell me what this means and what I'm meant to do?

Thanks
John

what are you buying and who from at what price.
darryl

USD3.5 I think it was. Who it was I can't remember

And what does it mean when they quote $3/pc

Means $3 dollars per unit or Item.