Orders can be submitted, revised and pulled either individually, or in batches. Batches have restrictions on them, such as limiting all the orders to the same account and market so are not suitable for all situations. However, if you are dealing with multiple orders at a time in the same account and market, such as market making, then batches of orders are significantly faster to process than individual orders so are strongly recommended in those circumstances. The rest of the time dealing with orders individually is much simpler.
NOTE: You must subscribe to the Account that you are submitting the order for otherwise you will not receive any order updates.
Single Orders
Batches of Orders