In order to be able to trade one currency for another, there must be a market (also known as a "currency pair") linking both currencies. In any currency pair, the price lets us know how much of the quote currency is required to buy one unit of the base currency. For example, a price of 1000 USD for BTC/USD means that 1000 USD is required to buy 1 BTC.
The first currency in a currency pair is called the base currency. For example, in the currency pair BTC/USD, BTC is the base currency.
The second currency in a currency pair is called the quote currency. For example, in the currency pair BTC/USD, USD is the quote currency.
Time in force is a special instruction used when placing a trade to indicate how long an order will remain active before it is executed or expires.
Buycoins has the following instructions available:
fill_or_kill: A Fill-Or-Kill order is an order to buy or sell that must be executed immediately in its entirety; otherwise, the entire order will be cancelled (i.e., no partial execution of the order is allowed).
good_til_canceled: A Good-Til-Cancelled order is an order to buy or sell that remains active until either the order is filled or the trader cancels it.