I understand that limit order is a threshold of price indicated by a buyer to a broker for executing the contract. Stop order definition also appears to be the same thing. Is stop order different than a limit order?

They are for different purpose.
I set up a limit order to prevent a situation so that I am not looted from the other side of the party. If I am making an order to sell, it will be above the current price.

I will setup a stop order if I beleive in momentum based directions. eg., if MSFT is 30$ today I will make a stop order to sell if MSFT goes below 25$. For example if it becomes 24.5 on one fine sunny day then my broker will sell it for 24.5. My thesis is that it will continue to fall, and I will make money when I cover up my short.

----------------
All my trading predictions are wrong. Now I want to bet against my predictions, because I am confident that I am a born loser. I am sure I will win this bet.

The only difference is in the purpose of the trade:

- Stop order is set to prevent the loss (you buy crude at 110 and set sell stop order at 100 OR you sell crude at 90 and set buy stop order at 100); however this price is not guaranteed, when the stop price is hit your order becomes market order meaning you (your trader) will get the best price available on the market at that moment...so stop order means you get the price desired or worse.

- Limit order is set to get the price that you want or better (so you buy oil at 110 and then you set sell limit order at 120 meaning you want to pocket the profit at the price of 120 or higher OR you short oil at 90 and then you set a buy limit order at 80 - again, you want to buy it back at 80 or lower).

There's also a stop-limit order: an order where limit order becomes active after stop order is hit.

Cheers B