With CFD trading a long position means a buy position that appreciates in value if the underlying market price increases. For example, of currency pairs: buying the base currency against the quote currency.
The quote currency is the second currency in the currency pair which can be bought or sold for the base currency.
Long position is the opposite of a short position.
Prior trading CFDs, make sure to understand how CFDs work. Do not underestimate the importance of education. Be aware leverage trading is risky.