On the left side of Figure 1, the magnified portion shows how each group of five holes is connected under the board. Each set of five holes are connected together by a piece of metal, as can be seen in Figure 2.
Note that the upper rows are separated from the lower rows by a gutter. There is no connections between the upper and lower rows (see Figure 2).
Across the top and bottom of the board are two long rows of holes. Each row is connected under the plastic by one piece of metal (see Figure 2). These are often used for multiple power supply or common connections.