Pressure is defined as force acting on a body per unit area.
P = F/A
Now when area increases, the force acts on a larger surface. Thus, ressure decreases.
Similarly, when area decreases, the same force acts on a smaller surface. Hence, the pressure increases.
Example 1: When you stand on snow with bare foot, your feet sink to a certain depth. However, if you wear snow shoes, your feet do not sink much. This is because area increased by snow shoes, and hence less pressure was exerted on snow.
Example 2: A nail is pierced in wall through its sharp tip and not through flat head.
Example 3: A sharp knife is able to cut vegetables better than a blunt knife.
Example 4: Trucks have pair of wheels instead of one wheel at one end. This is to increase the area and decrease the pressure on roads due to heavy weight of truck.
Example 5: If you press a board with finger, nothing happens. But, if you press a thumbtack with the finger and same force, then it gets inserted in the board.