All physically settled derivatives imply either an obligation to deliver, or take delivery of, a commodity at a location at some time in the future

The obligation to deliver a commodity is called a short position of that commodity at that location and time in the future

The obligation to take delivery of a commodity is called a long position of that commodity at that location and time in the future

Detail

Traders sum the position of a set of trades to know their net position across that group of trades - usually called a portfolio, a book or a strategy. This is known as the traded, or trader, position

Traders take a long position if they believe the value of the commodity at the time of delivery will be greater than the contract, or strike, price

Traders take a short position if they believe the value of the commodity at the time of delivery will be less than the contract, or strike, price. Taking a short position is sometimes known as shorting

Each time a trade is executed the trader's net position changes. Most traders update their net position as each trade is executed