Lot Size denotes the minimum transaction volume for a Forex trader. Different service providers offer different lot-sizes depending on their business needs and composition of their clientele. Some service providers might even offer their clients an option to choose their lot-size.
A lot-size of 100,000 USD is called “Major” while a lot-size of 10,000 is called a “Mini”. A client is allowed to trade only in the multiples of permitted Lot-size.