Eminis, sometimes referred to as emini futures are smaller units of older, "grown-up" futures contracts that have been around for quite a while. Emini contracts are still reliably new to the trading scene having arrived at it only a decade ago, while the "full" contracts have been around for longer than two decades.
There are several futures markets that have developed both full and emini contracts. The most popular of them is the S & P 500 futures whose emini contract is often denoted by "ES," its ticker. Another very popular emini contract, which was launched two years after the S & P 500 eminis is the NASDAQ 100 emini, frequently referred to by its ticker "NQ." Yet another one is Russell 2000, known among traders as "ER2." And while in real life situations these tickers may differ depending on your broker and even more on the charting platform you use, there is one thing all these contracts have in common: they all trade electronically on Globex, while their bigger "brothers" trade on The Chicago Mercantile Exchange (CME). There is one well known emini contract that calls the Chicago Board of Trade (CBOT) its home and that is the Dow Jones emini. It trades electronically just as the other mentioned above. Its often used ticker is "YM."
All of these eminis have yet another thing in common: they are futures contracts for stock prices. While there are now eminis for other futures in the markets that can be commodities (such as gold, silver or crude oil) or currencies (eg yen, euro), these newcomers are usually much less liquid then the stock index eminis and so trading them Can be much tougher if not much riskier. If you are just starting in this field, I suggest that you stick to the more established emini markets that guarantee better volumes and so also better trades due to better liquidity.
Stock index eminis are very often used for day trading which boils down to speculating in which direction the value (price) of their underlying index will move. If you expect it to move up, you buy one or more emini contracts and if the price indeed moves in your favor you can then unload these contracts for a profit. If you expect it to move down, you take a short position, selling emini contracts, and if you predicted the move right, you can brag about the dough you have made riding the move and exiting it at your target. Clearly, when your predictions do not pan out, you will end up with a loss. It is because of this speculation on which way the index will move that futures often lead the index price.
This price for some prices can be calculated to the second decimal point, but even in such cases the price of the related emini market changes by some larger fixed values known as ticks. For ES, 1 tick correspondents to $ 12.5 and one point consistants of 4 such ticks. For YM, the tick is the same as the point and both are equal to $ 5. When your position moves in your favor by 1 pt, you can make $ 50 in ES or $ 5 in YM per contract, assuming you are able to unload it after the move is over. Whether this is possible or not depends on your emini liquidity at the given (exit) price. Now, you should better understand why it is always a good idea to trade liquid markets. Simply because these markets allow you to take your profits (or losses) more easily.
The size of the profits you can make while day trading eminis is a function of the intraday range of your emini market. In ES, which average average intraday range is about 10 pts, the profits of 10 pts could in principle be possible, but in practice, because of the market unpredictability, most daytraders should be happy with a consistent daily profit of 2 pts which not infrequently is Made only after several trades. If the commission is included (around $ 5 per round turn for the average emini broker), this profit is less than $ 100 per contract and then in order to increase it most daytraders employ more than one contract in their trading.
How many contracts you can trade depends primarily on the emini margin which in turn varies from one broker to another. Some brokers out there, those who cater specifically to emini traders, set their daytrading margins as low as $ 500 per contract, and sometimes even lower. Most, though, require you to have at least $ 1000-2000 per contract in your account before you can trade. It is, however, highly advisable to have at least twice the margin per contract if you are to feel comfortable trading. Not all of your trades will be winners, you need to account for losers as well. Since the losers will cause drawdowns in your equity, you need to have some cushion to withstand them. Twice the margin is, in my opinion, the absolute starting minimum, three times is even better, particularly if you are a total beginner. In order to be allowed to trade, your equity must never fall below the margin level per contract. If it does, you need to reduce the number of contracts you trade and if this is not possible, you need to stop trading until you raise enough capital again.