“markets all around the world. additionally, us stock futures start trading earlier.”
Yes, but what do the futures consist of? In other words, if the nite before last on-line, I put in to sell x amount of share of a stock I own, and the markets didn’t open until this morning (Tuesday), are my shares I’m selling considered a future, as they were a pending sale until this morning? What is considered a future?
a future is a separate contract, related to a stock index as a whole, not to individual shares.
your stock trades as a stock when the stock market is open.
Futures are another way of trading things (stocks, stock indexes, etc. etc). Because they are an alternative market for the same or similar instruments (stocks, for example), their prices are indicative of the price of those assets (in the stock market, for example).
You could also trade stock futures and stock index futures if you were up for it, but it's generally a tool best left for professionals. and the entry fee is a bit high (as a it should be), because it's a much riskier market.