In recent years, Global and Grid Computing emerge as two powerful technology trends. In this paper, we compare these two approaches of distributed computing. First, we present a definition for Global Computing that accentuates the key point in this trend. This key point distinguishes Global Computing from other trends and covers many such systems. Second, we contrast two approaches in general characteristics. Then, by comparing them in technical issues, we show that the key point in our definition of Global Computing is the main source of many technical differences between these methods. Finally, we present our opinion about the probable future of Global and Grid Computing.