When you use a broker to invest in stocks and shares, you can enter into one of three types of arrangement with that broker, depending upon the type of service that you require:

If you want your broker to make all the investment decisions for you, so he decides what to buy and sell, and when to buy and sell, then you give him discretion and the arrangement is known as discretionary.

If you want to make all the investment decisions yourself but you want the benefit of your broker's advice before you actually give him a buy or sell instruction, then the arrangement into which you will enter is known as advisory.

If you want to make all the investment decisions and you just want to be able to call your broker and give him your instructions, then the arrangement into which you will enter is known as execution-only.