Futures tend to be a highly leveraged investment. They are normally settled in cash but there are some people who actually do hold them to term and take delivery of the asset. While they might have a somewhat complex name, a future is just basically a contract to buy or sell something at a certain price by a certain date.
In theory, they shouldn't affect the spot price of BTC. However, the price of BTC might be affected a bit to prevent people from making arbitrage profits between the spread between the futures price and spot price (current price) of BTC.
How does a contract get created. Do we need a seller and buyer to create a contract? Who issues the contract?