In contrast to finding an expert or two that seems to make valuable and careful decisions, do your best to avoid listening to share market 'tips' from friends or work colleagues. Typically these people will know less than you and have very little to base their suggestion on. No matter how well meaning it may be, advice from someone who knows next to nothing about the topic in question is not advice.
Limit order: A limit order differs from a market order in that the trade is only completed at a certain price. For example, if you enter an order to buy 10 shares of Nike at $70 each, the order will only go through if the broker can fill at it at a price of $70 per share. Limit orders are a good way to buy and sell stocks that trade less frequently, since there may not be enough willing sellers to fill a market order at a reasonable price. They are also good for stocks that you feel are too expensive right now, but that you'd be willing to buy if the price dropped. These orders are a good for "set and forget" investing, since you can place a limit order that will remain in effect until a stock reaches the price at which you'd like to buy.
A broker is simply a licensed person through whom you can buy and sell these stocks. When you use an online platform, it essentially acts as an online broker. If someone wants to buy any product, he can contact a brokerage service. They would place an order and let him know the market price of the product. If the investor is interested, they would include a commission for themselves and process the order forward. If the user wishes to buy stock, the broker would forward his order to a stock exchange, which would approximately take 3 days to complete including the money exchange between the broker and the investor.