Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

Do brokers execute every trade on the exchange?
There are two terms that are related, but separate here: Broker and Market Maker.  The former is who goes and finds a buyer/seller to buy/sell shares from/to you.   The latter (Market Maker) is a company which will agree to partner with you to complete the sale at a set price (typically the market price, often by definition as the market maker often is the one who determines the market price in a relatively low volumne listing).  A market maker will have as you say a 'pool' of relatively common stock (and even relatively uncommon, up to a point) for this purpose. A broker can be a market maker (or work for one), also, in which case he would sell you directly the shares from the market maker reservoir.  This may be a bad idea for you - the broker (while obligated to act in your interest, in theory) may push you towards stocks that the brokerage acts as a market maker for.