An Order is a set of instructions to a broker or brokerage firm to purchase or sell a security on behalf of an investor. Orders are the fundamental trading unit in the securities market and can be placed over the phone, online through trading platforms, automated systems, and algorithms. When an order is placed it goes through several steps before being executed.The first step in executing an order is for it to be routed from its originating source such as online platform or telephone call center directly into one of many different exchanges where securities trade. The exchange then matches buyers with sellers based on stock prices that match orders at their best price levels available at any given time during normal market hours depending upon liquidity conditions present within each individual exchange's marketplace . Once matched up by price level ,the buyer’s broker then submits this information back down stream so that they may complete their own internal bookkeeping processes associated with each transaction .Finally after all internal processing has been completed both parties involved will receive confirmation via email confirming successful completion of their respective trades along with other pertinent financial data related thereto . In conclusion , when investors place orders for buying and selling stocks they should understand what happens behind the scenes as well as how long it takes for these transactions to actually take effect within various exchanges across global markets today.