NSE or BSE??

what is the difference between trading in NSE and trading in BSE??? the share prices are almost the same but not the same in BSE and NSE..why is that?? can we buy in BSE and sell in NSE or vice-versa????

Slight difference(in paise) exists because both have different order books and traders. On certain occasions, the difference in the price may be large but the difference will last only for few moments as it will neutralized by arbitrageurs.

You can buy shares from one exchange and sell into another, provided you are selling from your demat account(already have delivery of the shares in your demat account).

If you are buying for intraday, or we can say, you wish to sell on the same day after buying, then you must sell on the same exchange. If you sell on the other exchange, you will not only have to take the delivery of bought shares, but also pay a penalty for not delivering the sold shares(shorting and auction).

You can also sell, and later buy(called as shorting). This one also has to be settled on the same exchange and on the same day. There is no concept of delivery in a short position. Settle the shares on the same day buy buying again(called as cover) else pay shorting penalty.