The full form of MIS is Margin Intraday Square off. You can use MIS order type when you take Intraday position.In MIS your order will remain activated till that particular day. The biggest advantage of MIS product type because of its margin. When you choose MIS as a product type and buying a any particular stock than you not need to pay full amount of that stock. You should only need to pay small amount or % of that stock. So by this, you would be able to buy large quantity of shares with lesser capital.
NRML or NORMAL
The full form of NRML is Normal Order. This order type is particularly used in future market or future contract. You should use NRML order type when you buy or sell a future contract and wanna carry around overnight or until the expiry of that contract. It is working same like a taking delivery of stock but you hold maximum till the expiry of that contract.
A Cover Order is any market order which is placed along with a Stop Loss Order. In a Cover Order, the buy/sell order is always a Market Order and is accompanied with a compulsory Stop Loss order, in a specified range. This Stop Loss Order cannot be cancelled.
Since the Stop Loss Order is being placed simultaneously while getting into the contract, the risk that is being taken automatically reduces. Because the risk reduces, the margin requirement also automatically reduces. Remember that all cover orders (CO) will be automatically squared off around 3:20 PM ., 11.15 PM and hence this is a good tool for Intraday traders only.